Cell Walls and Synthetic FibersMany theoretical chemists now discount much chemi-cal and botanical work in cell wall research before1920 and all current work which indicates the pres

-ence and importance of non-cellulosic materials indetermining cell-wall properties.

WANDA K. FARRCelane.ee Corporation of America

History and TerminologyTHE pioneer microscopist, Robert

Hooke (40), anticipated the discovery ofa process of synthetic fiber manufactureby more than two centuries with thestatement:

"—And I have often thought, that probablythere might be a way found out, to make anartificial glutinous composition, much resem-bling, if not full as good, nay better, than thatExcrement, or whatever other substance it be outof which the silkworm wire-draws his clew. Ifsuch a composition were found, it were certainlyan easie matter to find very quick ways of draw-ing it out into small wires for use. I need notmention the use of such an Invention, nor thebenefit that is likely to accrue to the finder, theybeing sufficiently obvious. This hint, therefore,may I hope, give some Ingenious inquisitivePerson an occasion of making some trials, which,if successful, I have my aim, and I suppose hewill have no occasion to be displeased".

In 1885 Count Hilaire de Chardonnet(15) obtained a British patent coveringthe first successful commercial processfor the preparation of "artificial silk."Plant fibers, after treatment with strongnitric acid, were dissolved under pres-sure in a mixture of alcohol and ether.The fine filaments of the extruded solu-tion were coagulated in water and sub-sequently denitrated by treatment withdilute nitric acid, chloride of iron andammonium phosphate. The final prod-uct was a glossy, flexible fiber possessingmany of the properties of silk.

The usefulness of plant fibers in thepreparation of "glutinous composi-

tions", from which textile filamentscould be spun, was shown concurrentlyin processes other than that described byChardonnet. In 1851 and 1857 it wasobserved (54, 65), apparently indepen-dently, that in ammoniacal solutions ofcupric oxide, plant fibers first gelatinizeand then disappear into a viscous fluid.In 1897 Fremery and Urban, under thename of Pauly (55), patented the firstcuprammonium process for fiber manu-facture.

In 1892 other investigators (20, 21)discovered that when cotton fibers aretreated with sodium hydroxide of mer-cerizing strength to form "soda cellu-lose" and this soda cellulose is thentreated with carbon disulfide, a so-called"cellulose xanthate" is formed. A solu-tion of this xanthate in dilute sodiumhydroxide has very high viscosities—hence the name "viscose". From thesolution the dissolved material may be re-covered in the form of textile fibers ormolded plastics. Its low cost and ver

-satility has assured its industrial im-portance.

Schutzenberger (64) treated cottonfibers with hot acetic acid anhydride andreported in 1870 the formation of "cellu-lose acetate". In his reaction mixtureshe recognized the formation of the triace-tat.e. Franchmont (29) in 1879 usedconcentrated sulfuric acid or zinc chlo-ride to catalyze the reaction. The proc-ess patented in 1906 (49) was an impor-

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CELL WALLS AND SYNTHETIC FIBERS

99

tant step toward the present industrialusage of acetone-soluble derivatives. Asdescribed recently (67)'Briefly the process consists in swelling thecellulose fiber so that all the hydroxyl groupsare available for acetylation. Acetylation iscarried out, using acetic acid anhydride and ace-tic acid with sulfuric acid or some other suitablecatalyst. The cellulose is acetylated to the tri -acetate and an excess of acetic acid is used as asolvent.

'"The cellulose acetate thus formed is thendeacetylated to the proper acetyl content. It isthen precipitated from the acetic acid solution,stabilized (if necessary), washed free fromacids and dried.

... In the utilization of cellulose acetatefor industrial fibers, in particular, it is necessaryto reduce the acetyl value so that the acetate be-comes soluble in acetone''.

The selection of a "trade name" forthese fibers has been described as follows(70) :

"For almost the whole of that fifty yearperiod, the several man-made fibers which sur

-vived the experimental stage and emerged intoa commercial world were called `artificial silks',a frank declaration of the motive which pro-duced them and of the light in which they wereviewed by the textile craftsman and the con-sumer. About twenty years ago the producersand merchants of these new members of the tex-tile family invented the generic term `rayon' toreplace the term `artificial silk'. . . . It was amoment of historic textile importance because itfirst emphasized that thesé man-made fibers, de-spite any outward similarity to silk, and despitethe natural tendency to use them in imitation ofsilk, were actually new and destined to stand orfall on their own distinctive properties andvalues''.

Names now used most commonly forman-made textiles, in which plant tissuesform the basic raw material, are "arti-ficial silk", "rayon" and "synthetic fab-ric". Although the suggestion has beenmade that the term "synthetic" be re-served for fibers such as nylon alone, nodecision has been made concerning ageneral terminology which will be accept-able to those concerned. The term "syn-thetic" now serves to distinguish, ingeneral, all man-made fibers from nativefibers such as cotton, silk and wool. In

the present article it applies specificallyto the "man-made'' textile filamentsmanufactured from plant cell walls.

Plant Fibers and Synthetic TextilesIt is worthy of particular considera-

tion from both the biological and the in-dustrial standpoints that, from all of theavailable plant tissues, fibers were chosenas the raw material for rayon manufac-ture. Seed fibers such as cotton, bastfibers such as flax, and wood fibers suchas are obtained from spruce and pine,are all characterized by the formation ofunusually thick cell walls. These wallsplay such an important role in determin-ing the physical and chemical propertiesof the natural fibers that the problemsconnected with processing for syntheticfiber production have dealt primarilywith cell-wall reactions to the reagents,temperatures, and pressures employed.

The substances which are commonlydescribed in cell walls, in general, maybe listed briefly as follows:

Ç crystalline1. Cellulose amorphous

f Pentosans2. Hemicelluloses j Galactosans

Mannosansf Protopectin

3. Pectic Substances j Pectinl Pectates

4. Lignin5. Suberin and Cutin6. Protein, resins, gums, coloring matter, tan-

nin, callose and minerals.

In the cotton fiber, materials fromgroups 1, 3, 5 and 6 are found. In bastand wood fibers of various types, ma-terials from all groups may occur. Inno cell walls are the different constitu-ents likely to be present in complete seg-regation, and the colloidal mixtures inwhich they naturally occur render theirseparation and identification difficult.

Plasticity and Deformability inNative Cell Walls

In the course of the manufacture ofsynthetic textile filaments, natural plant

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fibers lose their identity, and their walls,once tough and resilient, are transformedtemporarily into a soft continuous de-formable mass. From the view point ofindustrial processing, this phenomenonmay seem to be unique in cellular ex-perience, and the erroneous conclusionmay be drawn that living cells are notconfronted with the need for such prop-erties as plasticity and deformability.

Cells Without Walls. For more thana century it has been an accepted factthat 'the protoplast and not the cell wallis the essential part of a cell; that in thephenomenon of growth, the protoplastprecedes the cell wall; and that, in fact,the colloidal protoplasm is the stuff fromwhich cell walls are made.

In some cases, for the purpose of main-taining their plasticity and deforma-bility during important periods of theirlife history, protoplasts dispense withtheir cell walls. Close examination offallen tree trunks in a moist woodlandoften reveals strands of slime mould flow-in- slowly from the under side to the ex-posed surface of the log, the protoplastsunencumbered by cell walls. Othertypes of protoplasts first build heavy cellwalls and later emerge from the en-closure to continue their existence in anew locality. Observations of cells suchas these serve to emphasize the fact thatwhen there is a demand for the maxi-mum in plasticity and deformability, thecell either has no wall at all or uses awall only as a place of temporary abode.

Cell Walls and Cell Enlargement.In the process of growth, cells increase innumber by division. After cell divisionhas taken place the protoplasts of thedaughter cells often enlarge to manytimes their original volume, and theircell membranes are extended to accom-modate the increased surface area.

During this period of division and en-largement, they are known as "meri-stematic cells", and the region of theplant in which they are located is known

as the "meristem". Their cell walls arecharacterized by plasticity and extensi-bility, and chemical analyses show thatthese physical states are associated withcertain membrane-building materials. Inthis connection two authorities observe( 8`I):

"Macrochemical experiments prove the exist-ence of cellulose in the walls of the meristem,but its presence is masked by association withother substances.

Protein, closely linked to the cellulose, isfound by macrochemical experiments to be mostprobably the substance which prevents the re-action with iodine and sulphuric acid.

"Pectin is present in each case, though notdirectly linked to the cellulose in the meristemwall of radicle and root.

The middle lamella in the meristem is neverof calcium pectate but is probably a mixture ofpectin and. protein".

Microscopic and microchemical analy-ses of meristematic tissues indicate morespecifically the relation of the chemicalconstitution of young cell walls to theirobserved physical properties. In gen-eral, the primary wall is composed ofnon-cellulosic materials (26), and thisportion of the wall, not the cellulose-richsecondary lamellae, plays the active rolein cell enlargement.

Epidermal cells of the oat coleoptilerepresent a type in which cellulose isdeposited before • cell enlargement iscompleted (28). The enlargement takesplace in the original plastic membrane,however, and in the course of wall-elongation the cellulose is separated intohoop-like bands. The doubly refractivecellulose and the non-double-refractive,plastic materials of both the unelongatedand the elongated membranes, can be dis

-tinguished in polarized light. During alater period of growth these elongatedwalls are again made more rigid throughthe deposition of lamellae rich in cellu-lose between and within these separateddoubly refractive bands. Cells of dif-ferent types thus control their growtheconomy through the ingenious use ofnon-cellulosic and cellulosic materials.

CELL WALLS AND SYNTHETIC FIBERS

101

Cell Walls of Root Hairs and Cot-ton Fibers. Root hairs serve as uniqueexamples of the importance of non-cellu-losic materials in enlarging cell walls.Each hair is formed through the elonga-tion of a single epidermal cell of theroot; its function is the absorption ofwater and nutrient materials from thesoil. This absorption is facilitated by anintimate physical contact between theroot hair wall and the soil particles.Plasticity is again at a premium, and, inaddition, the cell wall must permit thepassage of aqueous solutions withoutbeing either dispersed or dissolved bythen.

Stier (78) - has found that stretching ofthe wall takes place more readily at thetip of the root hair than along the sides,and that when bursting occurs, the rup-ture is almost invariably at the tip.Cormack (19) has shown that these local-ized variations in hydrophilic propertiesare brought about by a decreasing degreeof calcification of the pectic materialfrone the base to the tip of the hair. Itfollows that the physical properties ofroot-hair walls are in large measure con-trolled by the chemical and physical stateof the pectic material which they contain.In most root-hair walls cellulose is notfound (41) ; when present it is reportedto be in the form of a very thin layerupon ' the inner surface of the primarywall of calcium pectate (60).

This type of wall composition is sharedwith primary walls of young cells, ingeneral. These are composed largely ofpectic material and protein (26), andcellulose deposition takes place towardthe end of the period ot cell enlargement,when loss of plasticity is no handicap.Root hairs represent a special group ofcells in which wall plasticity is of con-tinued importance, and cellulose forma-tion and deposition rarely take place.

The function of cellulosic and non-cellulosic materials in determining thephysical properties of native cell walls

is brought out even more clearly by adirect comparison of the cotton fiber andthe root hair. Both the hair and thefiber arise through the elongation ofsingle cells upon the surfaces of the rootand seed, respectively. The primarywalls of both are rich in calcium pectateand -contain little or no cellulose. In thecourse of the apical growth, the tips ofboth hair and fiber are less highly calci-fied than the lateral walls.

In later stages of development themarked differences between root hairsand cotton fibers appear. The proto-plasm of the cotton fiber produces largequantities of cellulose and uses it in theformation of many secondary lamellae;the protoplasm of the root hair produceslittle cellulose, and in many types it isentirely lacking. The cell wall of thefiber is thick and firm and is not easilydeformed; the cell wall of the hair re-mains more or less plastic and deform-able throughout its entire period of exist-ence. In the mature state the cell wallof the fiber contains a very high percent-age of cellulose and a low percentage ofpectic material, protein and wax (32) ;the mature root hair resembles, in struc-ture and composition, the primary wallof the fiber.

Examples may be drawn from variousparts of the plant kingdom to illustratethe fact that the properties of extremeplasticity and deformability are achievedin the native cell walls by the use of non-cellulosic materials; that membranes richin cellulose are no longer plastic; andthat extraordinary procedures are in-volved in reversing this state of rigidityin a mature cell wall. Industry reliesupon more or less drastic chemical andphysical processes. The cells themselvesusually bring about such reversalthrough the use of enzymes (17, 12).

These observed properties of fiber cellwalls and comparisons with the proper-ties of walls of other plant cells haveserved as a basis for some phases of the

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research dealing with the colloidal be-havior of cotton fibers and wood fibersduring the manufacture of synthetic tex-tiles. In the experiments attempts havebeen made to follow the various types ofcell wall components through their pro-gressive stages of reaction to reagentsused in xanthation, nitration and othertypes of industrial procedures. The re-sults, in turn, have been used in effortsto correlate the more fundamental as-pects of cell wall composition and struc-ture with the properties of fibers in boththe processed and unprocessed states.

Molecular and Colloidal Interpretationsof Structure and Physical Properties

Variations in experimental results anddifferent interpretations of chemical,physical and microscopic data have leftmany of the important considerationsundecided. The accumulated informa-tion has led, in general, to the develop-ment of two different viewpoints of thestructure of the native cell wall and therelation of wall materials to syntheticproducts. One interpretation holds thatthe cellulose molecule is the functionalunit which determines the properties ofnative cell walls as well as their syntheticderivatives. The other, following classi-cal colloidal lines, explains the sameproperties upon the basis of a hetero

-geneous chemical system, establishedthrough the vital activity of the colloidalprotoplasm and persisting in its moregeneral characteristics throughout the"purification" treatments involved inindustrial processing. For the purposeof discussion they shall be referred to asthe molecular and the colloidal inter-pretations.

Molecular Interpretations. Sponsler(75) developed in 1926 a conception ofnative cell wall structure which wouldaccount for the known properties-upona molecular basis. He expressed thebelief that X-ray diffraction data ob-tained from plant fibers could be ex-

plained by the presence of chains ofcellulose unit cells, of indefinite length,thus eliminating the necessity for con-sideration of the crystalline cellulose mi-cellae (molecular aggregates) of Nägeli(52). Staudinger (76) in 1934, uponthe basis of viscosity measurements, like-wise postulated the existence of very longmolecular chains of cellulose which hebelieved to be of sufficient size to warrantthe name "macromolecule". Others(35) in 1928 had questioned the in-definite length of the cellulose chains,had expressed the opinion that they arecomparatively short and that they arearranged in the form of a bundle or amicellar unit. Carothers (13) in 1931suggested a new type of organization ofcellulose chain molecules in the walls ofplant fibers in which the long axis of thechains is approximately parallel to thelong axis of the fiber, with pronouncedoverlapping of the ends of the chains.

Thiessen (81) described the new con-cept in 1938 as follows:

''The cellulose micelle is an ultramicroscopicmixed crystal of cellulose chains, differing inlength. Ends of chains project beyond themicelle ends formed by shorter chains (fringedmicelle). Because of the shorter filaments inter-posed in the micelle core, the fringes have suchlarge lateral distances that van der Waal'sforces no longer hold them together. For thisreason they tend to separate''.

This evolution of the molecular con-ception of cell wall structure is illus-trated in Figure 1. Adaptation of thehypothesis to the interpretation of thebehavior of both native and syntheticmaterials was described in 1938 - (31)

"A revision of the `Tägeli hypothesis of dis-continuous cellulose micellae was found to benecessary. Evidence was found of a system ofconnected cellulose threads or layers. Cellulose,in the form of long, chain-like molecules formeda skeletel framework. The molecular weightand length of the chains are not known. Theygive a crystalline X-ray pattern but never areseen in crystalline form. They are insoluble inall ordinary chemical solvents, but in reagentswhich will throw them into a viscous matrixtheir viscosities show that a fairly close relation

CELL WALLS AND SYNTHETIC FIBERS

103

J I I 11^a b

A B

Solution Coa6,u1ated OrientedD D D

FIG. 1. A. Parallel arrangement of chain molecules (a) and random arrangement of molecu-lar aggregates (b) (after Carothers). B. Fringed micelles according to the new theory (after

Kratky). C. Joining of two micelles by intertwining of fringes through Van der Waal•'s forces(after Kratky). D. Behavior of cellulose chains in a rayon-spinning solution, coagulated andoriented (after ifark).

exists between the strength of the whole fiberand the length of the cellulose chain molecules;maximum strength is believed to be reached inchains of about 2,000 glucose residues''.

One of the most recent reviews of thisfield of research was published in 1943in the form of a monograph prepared bya staff of specialists under the editorshipof Emil Ott (53). The size of the mono-graph indicates the rapid developmentof the molecular concept of cell wallstructure in the past 20 years. The view-point of the treatise is affirmed in the in-troduction as follows:

"It is the opinion of the editor that the pic-ture of cellulose , as a system of long chains ofanhydroglucose units is the most important con-cept in the book. From it may be derived, bythe application of ordinary chemical principles,an explanation for almost all the physical and

1 ''Cellulose'' and ''Chemical cotton'' areused synonomously in the molecular interpreta-tion of cell wall and synthetic fiber properties.Chemical cotton is prepared for industrial pur-poses from raw cotton linters by first partiallyremoving fragments of stems, seed coats, leaves,etc., by mechanical means, cooking in mild alka-line solutions, bleaching with chlorine, peroxidesor other reagents, washing thoroughly and dry-ing. The final product is fibrous and very muchwhiter than the original unpnrified linters.

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chemical properties of the molecule. . . . Cellu-lose tests have been assigned a relatively minorportion of the book because it is felt that thissubject is in a quite unsatisfactory state. Mostof the tests in common use originated in thedays before cellulose chemistry was well under-stood and have only empirical significance ".

The position now claimed for themolecular interpretation of cell wallstructure is evidenced by the following(53) :" On looking backward through the decadesfrom the vantage point of the present, it is easyto see that the chemistry of cellulose remainedat a virtual standstill from 1860 to 1920 becauseancillary sciences indispensible to the solutionof the problem, were in an undeveloped condi-tion. • By 1920 the labors of Emil Fischer andother investigations had placed the chemistry ofthe simple sugars upon a solid foundation. Themethylation method of determining the positionof hydroxyl groups in the carbon skeleton com-pleted its long apprenticeship, in the hands ofPurdie, Irvine, Denham, Woodhouse, and others,about the same time, and the essential, partlymethylated glucoses had been prepared andcharacterized. X-rays gave the first clear dif-fraction pattern of fibrous cellulose in 1920 andshortly thereafter the colloid chemistry'- oflinear micro-molecules, such as cellulose. provedto be, was very greatly clarified by Staudingerand his collaborators. These events make itconvenient to choose the year 1919 when EmilFischer died, as the beginning of the modernperiod of cellulose chemistry ".

These brief comments and quotationsserve to indicate the comprehensive ef-forts which are being made to interpretthe physical properties of cell walls andsynthetic materials manufactured fromcell walls, upon the basis of the molecularproperties of cellulose. As experimentalwork in this field continues, evidence ofmore and less highly reactive regions in

2 The chemistry of "high-polymers" or linear''macromolecules' is classified by Purves as abranch of colloid chemistry, and a "colloidalinterpretation'' in the sense used here is re-ferred to by Purves as the "AssociationTheory ". Experimental developments have thusserved to make the borderline less sharp be-tween the "molecular interpretation" and the"colloidal interpretation", and terms commonlyapplied to colloidal phenomena are found in dis

-cussions of both.

the wall material has led to a distinctionbetween "crystalline cellulose" and"amorphous cellulose" (11). In thepurification treatments for industrialprocessing, non-cellulosic materials areconsidered to have been removed com-pletely, and the factors concerned in thenitration acetylation, xanthation, etc., tobe those relating to the effects of proces

-sing upon the crystalline and amorphousstates of the cellulose alone.

In.the course of the development of themolecular interpretation of the structureand physcal properties of cell walls andsynthetic textiles, viscosity and X-raydiffraction measurements were originallyused as the experimental basis for theo-retical considerations (3, 35). The de-termination of osmotic pressures wasbrought into extensive usage later for asimilar purpose. Calculated values formolecular weights are obtained by meansof both techniques. The work in thefield of osmotic pressure determinationshas been reviewed comprehensively (87) .More recently a "Light-Scattering"technique has been used extensively. Areview of the theory of light scatteringhas been given (22, 90), and its appli-cation to cellulose acetate has also beenreported (77).

Colloidal Interpretations. Progressin the field of the colloidal interpretationof cell wall structure . and compositionhas been more or less continuous formore than a century. Lyngbye (45) ob-sérved "minutissime punctata" in thecell wall of a marine alga in 1819.Valentin (85) and many of his contem-poraries found that cell walls increase inthickness by the deposition of in iterialfrom the protoplasm upon their innersurfaces. In some cells they found mi-croscopically visible granules joined to-gether end to end to form fibrils which,in turn, were deposited as wall material.Others (1, 50) found that the fibrils ofthe cell wall are separable entities, andthat the spiral fibrils do not pass from

CELL WALLS AND SYNTHETIC FIBERS

105

one lamella to another. Schacht (62)showed that fibrils, when arranged inopposite directions in the membrane,have opposite properties in polarizedlight. The granules and fibrils, withtheir adhering protoplasmic materials,constitute a typical colloid system.These earlier workers were concernedwith the physical rather than the chemi-cal aspects of the system. Between 1840and 1860 others (e.g., 30, 56) mademany contributions to the chemicalnature of cell wall materials. Theyidentified "cellulose" and "incrustingsubstances", which interfered with thechemical reactions of the cellulose, andfound that cellulose, nitrogenous ma-terials, minerals And pectic substancescan be identified in most cell walls.Nägeli (52), using polarized light formicroscopic observations, discounted, inthe optical sense, the non-doubly re-fractive, gelatinous wall material ofFremy and Payen, and concluded thatthe cell wall is made up of microscopi-cally invisible crystalline "micellae"which are nearly contiguous; that bymoistening with water or aqueous fluidsthe surfaces of these micellae take upwater and the previously hard substancebecomes soft; and that, upon evapora-tion, the condition is reversed.

The "Micellar Hypothesis" was popu-lar and the conclusions of Payen andFremy were frequently overlooked untilMangin (47) published his valuable histo-logical memoires dealing with the heter

-ogeneous chemical nature of cell wallsin 1889. Strasburger (79) had found,however, that cell walls, in general, haveboth solid and gel-like constituents, thelatter in the form of a reticular colloidalframework; and that growth in thicknesstakes place by the deposition of gel andgranular "microsomes". Molisch (51)found that the microsomes are connectedby fine fibrils of protoplasm, while others(34, 82), in effecting the macrochemiealseparation of cell membrane constitu-

ents, found that the removal of massesof this colloidal gel brings about cell walldisintegration.

Farr and Eckerson (26) in 1934, bymeans of microchemical analyses and ob-servations in polarized light, determinedthe cellulose nature of Strasburger's gel-coated microsomes and the non-cellulosicnature of the gel itself. The microsomeswere renamed "cellulose particles" andthe gel "cementing material" (Figure2). Others (e.g., 36, 88) have describeda similar two-phase structure in cellwalls. Wieler compares the relation ofthe cellulosic and non-cellulosic mem-brane materials with that of the dropletsof honey in the honey-comb to the combitself. Hess and co-workers (37) havereported that fiber walls are made upmostly of crystalline cellulose sur-rounded by a thin sheath of other ma-terials which they have named "Haut-substanz ". They have concluded thatthe recognition of these two fiber com-ponents is important for the understand-ing of fiber structure as well as for re-actions to reagents. In both ramie andcotton fibers they have found that thenitrogenous "foreign substance" is fre-quently held fast during the purificationprocess. Farr and Eckerson (27) havereported that the purified state of cellu-lose is not approached until the fibrousstate is destroyed and the residue is inthe form of'a fine white powder. Thischange in physical state they havedescribed as "fiber disintegration,"brought about by removal of non-cellu-losic cementing material, and not as"cellulose degradation" which would in-volve changes in the crystalline celluloseitself. These findings have developedinto the conception that the fiber wall ismade up mostly of particulate crystal-line cellulose which diffracts X-rays andis doubly refractive in polarized light,surrounded by a thin sheath of non-cellu-losic material which is non-doubly re-fractive and amorphous. They are not

106 ECONOMIC BOTANY

Pia. 2. A (Upper left). Single cotton fiber with typical convolutions. B (Upper right).Fiber disintegration, showing individual fibrils and cementing material or ''Hautsubstanz'' ,

x 500. C (Center left). Disintegrating fiber washed with solvent for cementing material revealsparticulate structure of spiral fibrils. x 700. D (Center right). Later stage of fiber and fibrildisintegration. x 700. E (Lower left). Single fibrils composed of rows of cellulose particlesshow swelling and blue coloration in sulphuric acid and iodine. x 700. F (Lower right). Fibrouspectate prepared according to the method of Baier and Wilson. x 1,380.

CELL WALLS AND SYNTHETIC FIBERS

107

in keeping with the conception (7) thatthe cotton fiber wall is a continuousmatrix of cellulose, some portions ofwhich are denser than others, and thatthe Iamellate appearance of the wall isdue to alternating zones of dense and lessdense cellulose (43).

In 1938 Farr (24) described the col-loidal -reaction of the cotton fiber wallconstituents in cuprammonium hydrox-ide to be primarily that of the non-eellu-losic materials in which the cellulose par-ticles become dispersed. This result iscorroborated by some workers (9, 44)but is questioned by others (38, 39) whoconsider the reaction to be one of thecellulose component of the waII andaffirm the value of the measurement of

STRUCTURAL ELEMENTS DIAMETER

Primary wall * — 0.5 µLamellae — 0.2Fibrils — 0.2Fibril segments ~ 0.2Ground-fibrillae 80-150 A°Crystalline Micellae > 60 A0Molecule 4.5 A°

the cuprammonium viscosity of fibrousmaterials as a basis for determining themolecular weight of cellulose.

In 1939 Compton (18) reported astudy of the reactions of cotton fiber wallconstituents during the xanthation offibrous materials. The two-phase struc-ture of the wall was in evidence through-out, and the identity of the celluloseparticles was not destroyed during vis-cose formation.

Farr (25) described in 1941 the mi-croscopic aspects of the synthesis ofcellulose in cellulose-forming plastids ofliving cells. During the period of forma-tion the cellulose is surrounded by a col-loidal matrix rich in protein and pecticmaterial, and the final cell wall structureis the result of the organization of theseand other protoplasmic components intoa continuous, chemically heterogeneous,colloidal system.

Current Trends in the Interpretationof Structure and Properties

Hess (37) has recently confirmed hisearlier observations of a primary wall ofthe native fiber whose structure, com-position and texture are different fromthose of the secondary wall; and for thefibrils of the secondary lamellae, a sur

-rounding-membrane of non-cellulosicmaterial—probably pectin. He reports,in addition, a hitherto unobserved struc-tural element which he has named a"ground fibrilla". Its relation to theother structural elements can be seenfrom the accompanying table.

The "fibril segments" referred to inthis table correspond to the "micro-scomes" of Strasburger, the "cellulose

LENGTH LIGHT SOURCE

U. V. = 2750 A°U. V. n = 2750 A°

0.25 µ U. V. ,1 = 2750 A°(0.25 µ) Electronbeam1000 A° Cu Ka Radiation

Unknown

particles" of Farr and Eckerson and thesimilar structures described by Wieler inthe cells of the "honeycomb". The di-mensions as given by these authors are0.5 N, 1.1 x 1.5 p and 1.25 p respectively.Measurements made in fresh and driedmaterial, unswollen and slightly swollenstates, and in different optical systems,may account for these differences. Themeasurements of fibril segments weremade by Hess with an ultraviolet lightsource. The ground fibrilláe, into whichthe fibril segments separate, were observ-able only in the electron microscope be-cause of their diminutive size.

The ground fibrillae of Hess do notseem to correspond in their describedorigin and appearance with the ex-tremely fine fibrillar structures reportedin the electron microscopic studies of cellwall materials by others (8, 61, 66).These latter structures have more in corn-

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ECONOMIC BOTANY

mon with the anastamosing fibrils, someof which grade down to and beyond thelimits of microscopic visibility, describedby Bailey and Kerr.

The chemical nature of these fine anas-tomosing fibrillae is not decided. Thegroup of authors referred to above, alongwith Bailey and Kerr, have stated thatthey are cellulose. Wieler (88) reportssimilar structures in swelling reactionsof many types of cell walls and hasfound that they represent one of the col-loidal states of the continuous phase ofthe cell wall (honey-comb) in which thecellulose granules are imbedded. Others(6), in a discussion of "fibrous pec-tates", may have supplied a possible ex-planation of this finely fibrillar cellwall substance. Figure 2F illustrates afibrous pectate and its microscopic struc-ture, as observed in ordinary light. Asindicated by Wieler, such microscopicphenomena are not uncommon in themanipulation of cell wall materials. Ob-servation of the subdivision of fibril seg-ments into ground fibrillae would require,on the other hand, extremely carefulmanipulation of wall materials in allstages of preparation for electron micro-scopic observation. (36).

Hess reports, in addition, that syn-thetic fibers, beside the well known X-raystructure, have no macromolecular struc-ture which will compare with the in-genious structure of the natural fiber.He considers it likely, however, that insome cases of industrial processing, the''ground-fibrillae' are merely swollen,not broken clown, and are again recon-stituted in the process of coagulation.These observations, as well as others (18,24, 44), indicate the necessity for furtherstudy of the microscopic structure ofsynthetic fibers produced from cell walls,at all stages of industrial processing.

Still other workers (23) have con-tributed a detailed 'microscopic study ofswelling reactions of native fibers inacids and alkalis. From all types of

swelling and splitting observed, in whichwidespread disintegration of the swollenfiber takes place, small uniform-sized(0.5 x 1.5 p) particles were obtained inthe form of unswollen residues. In lesscompletely disintegrated fibers these par-ticles are seen with their long axesparallel to the fibril axis, and the authorsstate that they are probably identicalwith the "cellulose particles" describedby Farr. Continued treatment with hy-drolysing agents brings about disappear-ance of the particles themselves.

The nature and importance of the non-cellulosic constituents of both native cellwalls and processed materials has beenreflected in a number of recent studies:

Wurz and Swoboda (89),, applyingquantitative methods for uronic acids toeasily parchmentizable and bleached sul-fite pulps, found (calcd.7 galacturonicacid values of 2.05%-2.5%. Pulps thatshowed poor parchmentizability con-tained 1.4%-1.6%, and very poor pulps0.77%-0.94% galacturonic acid. Theauthors discount the possibility of theinfluence 'of oxycellulose in the pulp.Addition of calcium pectate to a pulpnot readily parchmentizable improved itsproperties.

The non-cellulosic incrustants in thejute fiber resemble, in their behavior,starch-size on a low-twisted, sized, cottonyarn, and while they themselves havelittle tensile strength, they contribute, ina marked manner, to the strength of thejute by cementing together the ultimatecellulose fiber bundles upon which thestrength fundamentally depends (59) .

The "hemicelluloses", named first(63) to denote a group of substances inthe cell wall considered very closely re-lated to cellulose and as intermediatesubstances in its development, are beingstudied intensively. Vincent (86) re-ports that while most hemicelluloses aresoluble in alkali, no alkali extraction everremoves all the hemicellulose fromfibrous material ; that hemicelluloses are

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not homogeneous, some fractions con-taining uronic acid, and that it is notsatisfactory to classify these non-cellu-losic materials as "hemicelluloses" and"polyuronides"; that hemicellulose inpulp gives added strength and less re-sistance to beating; that high hemicellu-lose content is not indicative of lowviscosity; and that it is demonstratedbeyond all reasonable dou^t that highhemicellulosic content is very desirablein wood pulps. Some (2) have isolatedand analyzed "hemicellulose" fractionsfrom aspen holocellulose. The resultsindicate the presence of galacturonic acidresidues, which makes it highly probablythat the fraction contains pectic ma-terial. Others (48) have found thathemicelluloses from liquefied tissues con-sist of uronic acid (generally d-glu-curonic) united to a seriés of d-xyloseunits with which d-glucose may be asso-ciated. They resemble gums and mucil-ages in that on hydrolysis they yieldsugar units and a more resistant por-tion, . an "aldobionic acid", which con-tains the uronic acid.

pH motility curves for "depectinized"cotton continue to shift as treatment with1% NaOH continues, and from the shapeof the curve they never reach a base line(72). The curve does not change inshape., after 16 hours. This indicatesthat some pectic material is retained, al-though previous work indicated that allwas removed after this length of treat-ment.

The electrochemical activity of col-lodion membranes depends entirely uponthe presence of impurities of an acidic(anionic) nature contained in the col-lodion used for their preparation (71).Active acidic impurities are largely dueto partial oxidation which occurs in themanufacturing, process, and partially dueto acidic groups which are present in thenative cellulose.

In the field of current research in themolecular interpretation of structureand properties, Seymour reports (68)

"Fibers are all high molecular weight prod-ucts and are related structurally to plastics andrubber. According to Mark the criterion whichdetermines whether a macromolecule is a rub-ber, a plastic, or a fiber is based upon its abilityto crystallize. If the chain-like molecules fitwell into the lattice they will crystallize and befiber-like. If the forces between the chains aregreater than 5,000 calories per unit mol, theproduct will exhibit the properties of a fiber.If the forces are less than 2,000 calories per mol,the product will be rubbery, and products hav-ing values in between will be plastics ".

•Gordon (33) points out the tendencyto study fundamentally the polymeriza-tion of single pure monomers, and, in thewords of Mark and Raff, "although co-polymerization is playing an increas-ingly important role in the preparationand technical production of high poly-mers, only very little is known about themechanism of this process."

"Recent Progress in Cellulose Chemis-try" (5) states that the most promisingadvance in studies of the degree of poly-merization of molecules is in the use ofcarefully fractionated samples. Calcula-tions by several different methods alllead to similar values which indicatethat the molecules are neither fullystretched nor randomly linked or coiled,but assume an intermediate shape ofmoderate undulation which becomes in-creasingly kinked as the degree of poly-merization increases. They add that itis important to determine the ratio ofamorphous to crystalline or ordered re-gions in cellulose, since the amorphousregions are more easily accessible tochemical attack, e.g., water uptake, ab-sorption of organic vapors and of dyes.

Fibers from SeaweedsOne of the most significant current

events in the field of research dealingwith cell walls and synthetic textiles isthe successful manufacture of "alginate"fibers. Under the title of "SeaweedRayon" Speakman (74) reviewed theprogress in this field in 1945. Tseng(83) in the same year helped to clarifythe confused viewpoints of these new

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products in a short article entitled "TheTerminology of Seaweed Colloids". Inconclusion he remarks:"In view of our incomplete knowledge oftheir chemistry it is still too early to proposea critical classification of seaweed colloids. Itmay be said, however, that there seem to be threegroups of phycocolloids. First of all, we havethe water-soluble ethereal sulfates as representedby agar, carrageenin, and fucoidin; they are.similar to mucilages in some of their properties.Secondly, there are the water-soluble reservecarbohydrates consisting exclusively of glucoseunits; they are represented by laminarin andoccupy a position similar to that of starch inland plants. In the third group we have thealkali soluble polyuronides, represented by algin,which are analogous to pectin".

A tentative systematic arrangement ofuseful seaweeds and seaweed colloidsgiven in diagrammatic form furnishesinformation , with which both biologistsand industrialists may conjure (83).The impressive array of cell wall ma-terials, the ease with which many of themmay be separated for identification anddetermination of physical properties,and their chemical relationships to thewall materials of fibrous cells of higherplants, indicate their value for studiesfundamental to the understanding ofboth native and processed cell wall ma-terials.

Of particular interest is the roleplayed by sodium and calcium in thecurrent manufacture of seaweed textiles.Speakman and Chamberlain (73), usingprinciples of current viscose practice, re-port that rayon of satisfactory appear-ance, handle and strength may be ob-tained by extruding a solution of sodiumalginate into a coagulating bath of N cal-cium chloride, 0.02 N hydrochloric acidand 2.5% by volume of olive oil emul-sified with an agent such as Lissapol C.In a later paper Chamberlain and co-workers (14) state that calcium alginateyarn seems to be suited as the stock ma-terial for all purposes. It can be con-verted into woven or knitted fabricswhich can then be made alkali-resistant

in finishing by forming chromium orberyllium alginates.

These reactions of seaweed colloidssuggest the value of comparisons withthe reactions of the pectic material ofhigher plants (6) as well as the impor-tant functions played by calcium in themembranes of living cells. That suchcomparisons have . given and stillare giving pause in theoretical develop-ments is indicated in the following quo-tation (4) :"The fibrous poly-saceharide from seaweed,alginie acid (poly B-niammuronie acid), givesan excellent X-ray fiber photograph, but con-trary to expectation the period along the fiberaxis is not the same as that of cellulose (10.3 A),but 8.7 A°, in spite of the fact that the chainmolecules are undoubtedly in a fully extendedconfiguration. The unification here consists inexplaining this paradox in terms of one and thesame set of postulates, viz., the ordinary ac-cepted inter-atomic distances and bond angles.In both cases the ring is the Sachse "arm-chair", but at the two ends of this armchairthere are two possible directions of the glu-cosidie oxygen bond: one holds in celluloseand the other in alginic acid. Either config-uration may pass to the other by virtue ofintramolecular oscillations, from which it fol-lows that 10.3 is not the prerogative of celluloseand the 8.7 period is not the prerogative ofalginic acid. It is now conceivable that deriva-tives of either may be found, under the rightconditions, to have either period. Neither arethese two periods characteristic of B residuesonly, for the alginic acid configuration is ap-parently assumed also by pectin, which is builtfrom d-galacturonie acid residues".

It is to be expected that, from the in-dustrial development of seaweed textiles,valuable information concerning themany types of cell wall constituentsthere represented, and their relation tothe physical properties of both the nativeand processed states, will be more clearlyunderstood. It is to be hoped that all ofthe valuable techniques which have beendeveloped in connection with both themolecular and the colloidal interpreta-tions of cell wall composition will bebrought to bear upon the problems to theend that the properties of cell wall corn-

CELL WALLS AND SYNTHETIC FIBERS

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ponents throughout the plant kingdommay be more accurately appraised.

ConclusionThe biologists, chemists and indus-

trialists of the past century based theirinterpretations of the nature of cell wallsand synthetic textiles upon chemicalanalyses, microscopic analyses and thegeneral colloidal behavior of the ma-terials exhibited in their native and pro-cessed states. The investigations of thepresent century have added to these themore or less generally used techniquesof X-ray diffraction (3), refinements inviscosimetry (76) and osmometry (87) ,electrophoresis (46), ultra-centrifuga-tion (57), electron microscopy (58),ultraviolet microscopy (37, 69), micro-radiography (16), microincineration(80), phase difference microscopy (10)and the production of crystalline galac-turonates (42). It is encouraging tonote that data obtained by means of thesetechniques are being used in both themolecular and the colloidal interpreta-tions of the properties of cell walls andsynthetic textiles. The intensive re-search now in progress and carefulevaluation of the data obtained may lead,within this century, to the solution ofmany of the problems in structure andcomposition which are here outlined andbriefly discussed.

Summary1. The manufacture of synthetic tex-

tiles was anticipated by Robert Hookein a treatise on microscopy published in1665.

2. Researches of John Mercer,Edward Schweizer, and contemporaryworkers laid the foundations of presentindustrial practices during the middle ofthe nineteenth century.

3. In 1885 Count Hilaire de Char-donnet obtained a British patent cover-ing the first successful commercial pro-cess for the preparation of artificial silk.

4. Man-made fibers are currentlymanufactured from plant cell-wall ma-terial under such technical names as"cellulose nitrates", "cellulose ace-tates", "cellulose xanthates" and "cup-rammonium mellulose".

5. The trade names "artificial silk","rayon" and "synthetic fibers" areapplied, upon occasion, to any one ofthese processed forms. The terminologyis confused, and efforts are being madeto clarify it.

6. Plant fibers are used almost ex-clusively for the manufacture of syn-thetic textiles, although seaweeds are nowbeing processed for, similar purposes.

7. In the production of man-madefibers the art has preceded the science,and the structure and composition ofboth native and processed materials arenot clearly understood. Accumulatedinformation has led to the developmentof the "molecular" and the "colloidalinterpretation ".

8. The molecular interpretation holdsthat the cellulose molecule is the func-tional unit which determines the proper-ties of native cell walls as well as theirsynthetic derivatives. The colloidal in-terpretation explains the same propertiesupon the basis of a heterogeneous chemi-cal system, established through the vital_activity of the colloidal protoplasm, andpersisting, in varying degrees, through-out the treatments involved in industrialprocessing.

9. Examples from various parts ofthe plant kingdom reveal the fact thatthe - properties of plasticity and deform-ability are achieved in native cell wallsthrough the use of non-cellulosic ma-terials; that membranes rich in celluloseare no longer plastic; and that extra-ordinary procedures are involved in re-versing this state of rigidity in the ma-ture cell wall. Industry relies uponmore or less drastic chemical and physi-cal processes; the cells themselves bring

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1. Agardh, J. G. De cellula vegetabili fibrillistenuissimis contexts. 1852.

2. Paper Ind. & Paper World 27: 1037. 1945.3. Astbury, W. T. Fundamentals of fiber

structure. 1933.4. Jour. Textile Inst. 36: 154. 1945.5. Ind. Eng. & Chem. 37: 227. 1945.6. Ind. Eng. & Chem. 33: 287. 1941.7. Jour. Arn. Arb. 16: 273. 1935.8. Am. Dyestuff Rep. 31: 254. 1942.9. Kolloid Zeits. 36: 17. 1925.

10. Sei. Mo. 63: 191. 1946.11. Am. Jour. Bot. 29: 416. 1942.12. Dept. Sei. & Ind. Res., London, Spec. Rep.

33. 1929.13. Chem. Rev. 8: 353. 1931.14. Jour. Soc. Dyers & Colourists 61: 13. 1945.15. "Artificial Silk". British Patent No.

6,045. (1885).16. Colloid chemistry (Alexander) Vol. 5: 146.

1944.17. Chem. & Ind. 61: 518. 1942.18. Ind. Eng. & Chem. 31: 1250. 1939.19. Am. Jour. Bot. 32: 490. 1945.20. Berlin, Chem. Ges., Ber. 26: 1090. 1893.21. U. S. Patent 520,770, June 5, 1894. British

Patent 8,700, Feb. 6, 1893.22. Jour. App. Physics 15: 338. 1944.23. Dolmetsch, H. et al. Zusammenhänge

zwischen morphologischen Bau and Re-aktionsweise technicker Zellstoffe. 1:167. 1944.

24. Contr. Boyce Thompson Inst. 10: 71. 1938.25. Contr. Boyce Thompson Inst. 12: 181.

1941.26. Contr. Boyce Thompson Inst. 6: 189. 1934.27. Contr. Boyce Thompson Inst. 6: 309. 1934.28. Contr. Boyce Thompson Inst. 10: 127.

1939.29. Berlin, Chem. Ges., Ber. 12: 1938. 1879.30. Comp. Rend. Acad. Sei., Paris 48: 319.

1859.31. Nature 142: 899. 1938.

Jour. Agr. Res. 36: 471. 1928.Chem. & Ind. 46. Nov., 1945.Jahresbericht 1: 85. 1885.Zeits. Krist. 69: 271. 1928.Ber. Deut. Chem. Ges. 72: 642. 1939.Melliand Textilber. 24: 280, 333. 1943.Ind. Eng. & Chem. 33: 868. 1941.Textile Res. 10: 323. 1940.Hoo}ce, R. Micrographia. 1665.Bot. Gaz. 72: 313. 1921.Nat. Bur. Stand., Jour.. Res. 32: 77. 1944.Protoplasma 27: 229. 1937.Am. Chem. 528: 276. 1937.Lyngbye, H. C. Tentamen hydrophy-

t9logiae danicae. 1819.Colloid chemistry (Alexander) Vol. 5: 387.

1944.47 Comp. Rend. Acad. Sci., Paris 109: 579.

1889.48. Jour. Chem. Soc. London 796. 1945.49. U. S. Patent 838,350, Dec. 11, 1906.50. Mohl, H. von. Principles of the anatomy

and physiology of the vegetable cell.Trans. by Arthur Humfrey. 1852.

51. Molisch, H. Grundriss einer Histochemieder pflanzlichen Genussmittel. 1891.

52. Sitzungsber. Bayerische Akad. Wiss.München 1: 282. 1864.

53. Ott, E. Cellulose and cellulose derivatives.1943.

54. Parnell, E. H. The life and labours ofJohn Mercer. 1886.

no. British Patent 28,631. 1897.56. Payen, H. Mémoire sur les dévéloppements

des végétaux. 1842.57. Colloid chemistry (Alexander) Vol. 5: 411.

1944.58. Colloid chemistry (Alexander) Vol. 5: 146.

1944.59. Jour. Textile Inst. 35: T93. 1944.60. Bot. Gaz. 62: 488. 1916.61. Kolloid Zeits. 93: 163. 1940.62. Schacht, H. Beiträge zur Anatomie und

Physiologie der Gewächse. 1854.63. Zeits. Physiol. Chemie 16: 387. 1892.64. Chim. Physiol. 21: 235. 1870.65. Jour. Prakt. Chemie 72: 109. 1857.66. Paper Trade Jour. 114: 43. 1942.67. Colloid chemistry (Alexander) Vol. 6: 886.

1946.68. Am. Dyestuff Rep. 35: 128. 1946.69. Shillaber, C. P. Photomicrography in

theory and practice. 1944.70. Rayon Textile. Mo. 26: 59. 1945.71. Jour. Physical Chem. 49: 47. 1945.72. Nat. Bur. Stand., Jour. Res. 26: 65. 1949,73. Jour. Soc. Dyers Col. 60: 264. 1944.74. Nature 155: 655. 1945.75. Jour. Gen. Physiol. 9: 677. 1926.76. Cellulose Chem. 15: 53. 1034.

about such a reversal through the use of 32.

enzymes. 33.

10. It is to be hoped that all of the 3}'35.valuable techniques which have been de- 36.

veloped in connection with both the 37.

molecular and colloidal interpretations 38.

will be brought to bear upon the prob- 40.lems of current importance to the end 41.that the properties of cell walls and syn- 42.thetic textiles may be more accurately 43.

appraised. 44•45.

Bibliography 46.

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77, .Tour. Am. Chem. Soc. 68: 159. 1946. 84.78. Stiehr, G. Das Verhalten der Wurzelhaare 85.

gegen Lösungen. 1903.79. Strasburger, E. über den Bau und das 86.

Wachstum der Zellhäute. 1882. 87.80. Am..Jour. Bot. 30: 447. 1943.81. Aug. Chem. 51: 315. 1938.82. Tschirch, A. Angewandte Pflanzenanato- 88.

mie. I. 1889. 89.83. Science 101: 597. 1945. 90.

Proc. Royal Soc. London B95: 109. 1923.Valentin, G. Repertorium für Anatomie

und Physiologie. 1937.Paper Trade Jour. 122: 53. 1946.Wagner, R. H. Osmotic pressure determi-

nations. Physical methods in organicchemistry. Vol. 1: 253. 1945.

Protoplasm 34: 202. 1940.Papier-Fabr. 37: 120. 1937.Polymer Bull. 1: 90. 1945.

Utilization Abstracts

The Shelterbelt Project Pronounceda Success. In 1934 the most ambitious utili-zation of living trees and shrubs ever con-ceived to diminish the injurious effects of ad-verse climatic conditions, was instituted in theUnited States as the Prairie States ForestryProject and thereafter popularly known asthe Shelterbelt Project. "Its chief purposeswere, through tree planting, to amelioratedrought conditions, protect crops and live-stock, reduce dust storms, and provide usefulemployment for - a drought-stricken people"in -a strip of the country extending fromCanada through North and South Dakota,Nebraska, Kansas and Oklahoma into centralTexas.

The idea originated with President Frank-lin D. Roosevelt in 1932 and its executionwas stimulated by the drought . and duststorms of 1934. It was planned and carriedout bv the U. S. Forest Service and SoilConservation Service, almost exclusively onrelief funds, beginning in 1935 and continu

-ing until 1943 when the `Yorks Progress Ad-iuinistration was terminated. On the basisof extensive preliminary studies, the projectwas pursued from 1935 through 1942 byplanting 220 million trees and shrubs in30,223 belts on 33,000 farms, the belts cov-ering 238,000 acres and totaling 18,600 milesin length. Most of the belts were alongproperty lines and varied in length from one-eighth to one, and in a few instances to two,miles. Within the belts the number of rowsof trees and shrubs varied from one to 56.The rows within the belts were from eight to14 feet apart, and the trees were from sixto eight feet apart, the shrubs from two tofour feet apart.

In 1944 a survey was made in order to ap-praise the results of the project. Of themore than 30,000 belts originally planted,1,079 were examined, or 3.6%, which repre-sented 2.7% of the total mileage and about3% of the 220,000,000 trees and shrubs.Many features were taken into considerationin this survey and a detailed report renderedon the survival of the 44 kinds of trees andshrubs planted. These notes constitute arésumé of that report, excerpts from thesummary of which are:

"In terms of meeting the main purpose forwhich the belts were established, that of pro-tection against wind, the Project was a suc-cess. For the area as a whole, 78.4 percentof the belts were rated as good or better, andonly 10.4 percent as unsatisfactory, Treesurvival throughout the entire area coveredwas generally good. Survival of those spe-cies which were planted in more than 100rows (probably also in more than 100 belts)ranged from 39.2 percent for ponderosa pine(267 rows), the pooresb, to 85.0 percent forbo xelder (159 rows), the best.

"Benefits which have already been derivedfrom the program include landscape im

-provement, control of wind erosion, snowtraps along highways, protection of farm-steads, gardens, orchards, and feed lots, pro-viding a haven for game and song birds, fur-nishing wild fruit for preserves, providingfence posts and small poles for use on thefarm, and bringing new districts into the soilconservation program.

"The Shelterbelt Project has been a suc-cess." (E. N. Manns and J. H. Stoeckeler,Journal of Forestry 41: 237. 1916).

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Chemical Utilization of Wood. Thevery important problem of profitable utiliza-tion of the huge amount of wood annuallywasted in the United States is one of thechief concerns of the Forest Products Lab-oratory, operated by the U. S. Forest Serviceat Madison, Wisconsin. While the Labora-tory's approach to the problem is from thechemical standpoint, it is recognized that"economical harvesting and transporting ofwood waste so that it can be deliveredcheaply for chemical use seems to be the big-gest obstacle confronting the chemical utili-zation of wood".

Such chemical utilization of wood wastemay be divided into six categories, viz., pulp-ing, extraction, hydrolysis, destructive distil-lation, reactions with various chemicals, andchemical treatment to improve the qualitiesof wood.

Pulping yields not only paper pulp on alarge scale but also tannin from chestnutchips on a smaller scale. Waste liquors frompulping processes are sources of solublelignin, hemicelluloses and wood extractives,all of considerable potential value. Turpen-tine and tall oil are now being recovered toa limited extent from the sulphate pulpingof southern yellow pine. Tall oil is used indrying-oils and soaps. Sulphite waste liquorfinds some use as a dust settler for roads.Lignin is serving as a dispersing agent forcement in the making of concrete, and is be-ing incorporated in the negative-plate pasteof electrical storage batteries; it also findsuse in the manufacture of vanillin, the activeconstituent in vanilla extract. Soda-milllignin may become useful for laminatedplastics without addition of auxiliary resin,and it has been shown to be useful as aphenolic-resin diluent. The hemicelluloses areconverted almost entirely to sugars in thesulphite process, and those sugars, to some ex-tent, are being fermented to ethyl alcohol andused for grówing yeast.

Extraction processes still await much de-velopment and can be profitably applied atpresent to only a few species, yielding, inparticular, turpentine and rosin from south-ern pine stumps, and tannin from chestnutand hemlock.

Hydrolysis of the carbohydrate portion ofwood to sugar, and then fermentation of thelatter to alcohol, represent the generalized

process of manufacturing ethyl or grainalcohol from wood waste. "If all the sulphiteliquor from pulp mills producing more than100 tons of pulp a day were fermented, alco-hol production from this source would beabout 30 million gallons of alcohol per year,which is about 3 percent of the present an-nual production." Such manufacture mustcompete with alcohol production from grainand possible production from petroleum.

Fermentation of wood sugars can also pro-duce acetone, butanol, 2,3-butylene glycol andlactic acid, useful as solvents and as rawmaterials in making synthetic rubber andplastics. And fodder yeast can be grownon the total sugars as well as on the stillbottoms.

Destructive distillation of wood, formerlyan industry of some size, has dwindled sincedevelopment of the present method for mak-ing synthetic wood alcohol, and revival ofthe industry is dependent upon the develop-ment of new techniques.

Studies in the hydrogenation of wood haveshown that lignin dissolved in organic sol-vents or suspended in water can be made toreact with hydrogen gas, producing newcyclic alcohols that show promise as plasticsolvents, antiknock agents for motor fuel,and toxic agents.

Lastly, there is the production of modifiedwoods through treatment with resins and inother ways. (A. J. Stamm, Journal of For-estry 44: 258. 1946).

Sunflower Seeds. Sunflower seeds con-tain 32%-45% of edible oil, and the plantshave long been extensively grown in theU.S.S.R., Roumania and Argentina for pro-duction of oil. More recently the crop hasmade headway in the U.S.A., Canada, Uru-guay, Hungary, Rhodesia and other lands.In 1940, under the impetus provided by thewar through a decreased supply of vegetableoils, experiments were undertaken in GreatBritain toward raising the plants as a sourceof oil. The results so far indicate that theycan be commercially' grown and utilized there.A book of 155 pages and 20 plates has re-cently been published in London on the sub-ject: Hurt, E. F.—Sunflower for food, fod-der and fertility.

Sunflower oil is a semi-drying oil equal tothe best olive oil in its medicinal and feeding

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value for human consumption. It is excellentfor margarine and salad oil and as a substi-tute for cooking lard. The seeds make goodpoultry feed and the residue from oil extrac-tion is a valuable livestock feed.. (TV. B.Brierley, Nature 157: 604. 1946) .

Medicinal Plants. In northeasternUnited States—New Jersey, New York andall the New England states—there are 67wild species of herbaceous plants (listed inthe article) possessing medicinal propertiesthat might serve as commercial sources ofdrugs, but which have not yet been used assuch, not even in the recent war emergency.So far as Maine is concerned, for instance,only a little collecting of juniper terries andof lycopodium spores has been profitablyconducted by a few individuals.

Cultivation of drug plants in the area, ex-cept for temporary spurts, has degreasedsince World War I. In 1918, for example,four growers in New Jersey raised bella-donna on about 35 acres; in 1941 the acreagewas practically nil. In some other states,however, including Wisconsin, Pennsylvania,Virginia, Tennessee and Ohio, belladonnawas harvested on 400 to 500 acres in theautumn of 1942 as a result of seed distribu-tion by the U. S. Department of Agriculturein the spring of that year.

At least nine other kinds of drug plants(listed in the article) were found in approxi-mately 2,400 nurseries, but of them only Con-vallaria was being raised in considerablequantities. (R. H. Cheney, Bull. Torrey Bot.Club 73: 60. 1946).

Pre-harvest Fruit Drop. In 1939 itwas announced that premature fruit dropcan be prevented in fruit trees by use ofhormone sprays, and by 1942 commercial useof such sprays had developed to the extentthat 75,000 to 80,000 acres of apples weretreated that year in the United States. Morerecently experiments have heen conductedduring five seasons on the use of such sprayson five varieties of apple and one of pear atthe East Mailing Research Station, England.a-naphthaleneacetic acid in concentrationsranging from 2.i, to 10 p.p.m. were tried. Alarge significant gain in erop was obtainedwith the pear and three of the apple varieties.(111. C. Vycyan, Jour. Porn. C Hurt. Sci. 2:11. 1946).

Peanuts. At the Southern Regional Re-search Laboratory, New Orleans, a compre-hensive investigation is under way concern-ing the industrial utilization of peanuts. Anexcellent account of this work was publishedlast year, and these notes are based on thatreport.

The increased demand for new sources ofoil that resulted from the recent war was inpart responsible for stimulating the Amer-ican peanut industry to such a degree thatduring the war it experienced a five-fold in-crease in cash value, finally bringing an esti-mated $200,000,000 annually to Southernfarmers who produce the crops, and makingpeanuts in 1945, for the first time, the num-ber one cash crop in Georgia.

Industrial utilization of peanuts, alwayssecondary in importance to their use as food,involves, primarily, crushing them' for oil anduse of the residual high-protein meal as live-stock feed. For these purposes peanuts arenormally used that do not meet food qualitystandards or that are in excess of food re-quirements.

In 1940-41 35% of the peanut crop wascrushed, producing 171,000,000 pounds of oiland 260,000,000 pounds of meal. Of thisproduction 75% to 90% of the oil was con-sumed in the manufacture of shortening andoleomargarine; all the meal went into live-stock feed.

The industrial problems awaiting solutionare concerned in part with finding uses forthe by-products of the food- and oil-produc-ing processes, namely, the hulls, skins andembryos, and with obtaining greater extrac-tion of oil—from 5% to 9% of it remainsin the meal with present customary methodsof hydraulic pressure. About 30,000 tons ofhulls and 12 to 15 million pounds each ofskins and . embryos accumulate annually' inthe United States as by-products of themajor industrial processes. The manufactureof peanut butter is the principal source ofskins and embryos. Solvent extraction of theoil is not commercially employed in this coun-try, though that method leaves as little as 1%of oil in the meal.

About 90% of the peanut oil producedin this country goes into edible prod-nets, principally vegetable shortening andoleomargarine. Sinne dues into salad andcooking oils. Other uses of the oil includethe manufacture of soap and shaving cream,

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face creams and other cosmetics, and phar-maceutical preparations. And still otheruses, minor in importance and still more orless in experimental stages, are as a massageoil in the aftertreatment of infantile paraly-sis; as a carrier of drugs, such as adrenalinand penicillin; in boring compounds, oilsprays and insecticide emulsions; as a textileor other lubricant; for leather impregnation;as a Diesel fuel; and as a gasoline and kero-sene substitute. The oil is not suitable, how-ever, in the manufacture of mayonnaise andsalad dressings, for it may not remain com-pletely fluid at refrigerator temperatures.

The Southern Research Laboratory is con-cerned with the development of all these andother possibilities, as well as with the preps-ration of peanut proteins which may becomethe basis of textile fibers, adhesives, coatings,sizes and plastics, and a possible source ofamino acids. In England peanut proteinfiber has been marketed under the nameArdil. (C. L. Wrenshall, Chemurgic Digest5(9): 157. 1946).

Shelterbelts in Russia. In the subtropi-cal districts of Georgia, U.S.S.R., there aremiles of tree shelterbelts planted to protecttea and citrus plantations against wind.Some of them are 10 to 12 years old withtrees up to 35 feet in height. The best treesfor this purpose have been found to beSequoia, Cryptomeria, cypress, tulip, planeand poplar, the most profitable of all, inview of its also furnishing much cordwood,being Cryptomeria. In addition to providingshelter the various species also furnish woodand serve as sources of essential oils andresins. (N. Yushkevich, Journal of Forestry41: 206. 19.16).

Castor Beans. In 1850 there were 23castor oil mills in the United States—inIllinois, Missouri, Virginia, Tennessee, Penn-sylvania, Alabama and Arkansas. St. Louiswas the commercial center of the industry.In 1870 there were only six mills in opera-tion, in Texas, Missouri, New Jersey andTennessee. In 1880 the domestic productionof castor oil amounted to nearly 24 millionpounds, and an additional 2.1 million poundswere imported. Thereafter domestic produc-tion dropped, reaching about 20,000 poundsin 1920, and today there is not any commer-cial castor bean production in this country.

By 1940, however, importations of the beanshad increased to 3071 million pounds, andthe mills handling these importations todayare on the East coast.

India formerly was the great source of cas-tor beans, but production has shifted to the

New World, and during the recent war im-portations into the United States were almostentirely from Brazil and Mexico.

From the leaves of castor plants theWoburn Chemical Corporation has developedan insecticide, Spra-Kast, and the stems area source of pulp and cellulose which can beused in making cardboard containers, wall-board, newsprint and kraft and other papers,provided the economics of handling make itprofitable. . Oil is extracted from the seedsor beans, and the remaining pomace, whichcontains a poisonous substance that makes itunsuitable as livestock feed, is used as ahigh-nitrogen fertilizer.

It is the oil, pressed from the seeds, thatis the important and commercially valuableproduct of the plant. It enters into themanufacture of at least 25 kinds of products(listed in the article), and the foremost newdevelopment in its utilization is the produc-tion of hydrated castor oil, used as a fastdrying oil for paints and varnishes. Thishydrated oil accounted for 64 million of the77 million pounds of castor oil used in 1944.Other quantities are converted into sebasicacid and capryl alcohol for the plastics in-dustries.

Establishment of an American castor beanindustry and independence of foreign sourcesinvolves solution of various harvesting andhandling problems, and to this end the ser

-vices of plant breeders as well as engineers isneeded. Breeding work can contribute byproviding strains of suitable height with finesteins and capsules that do not drop or shat-ter too readily; in short, varieties that willbe high-yielding, non-shattering, disease-re-sistant and adapted to mechanized handling.Work along these lines was conducted by theU. S. Department of Agriculture in 22 Statesin southern parts of the country in 1941,1942 and 1943, and similar work is beingcontinued at the Bureau of Plant IndustryStation, Beltsville, Md., at the University ofNebraska, Louisiana State University and theIllinois Agricultural Experiment Station.(R. 0. Weibel and W. L. Burlison, ChemurgicDigest 5(9): 167. 1916).