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Page 1: The genus  Micromeles  revisited

i l IA)SLAV KOVANDA l and JAMES CItALLIC:E 2

t Botanical Ins t i tu te , Czechoslovak Academy of Sciences, 252 43 Prflhonice near Praha, Czechoslovakia 2 Long Ashton Research Station, Universi ty of Bristol, BS18 9AF, England

T h e g e n u s Micromeles r e v i s i t e d

K e y w o r d s

Sorbus L. emend. CRA~TZ, Micromeles DECAISNE emend. KOEHNE, Raphiolepis LINDL., Leaf venation, Flower and fruit morphology, Generic limits in the Mcdoideae, Chemotaxonomy, Flavone C- and O-glycosides, Phylogenetic implications

A b s t r a c t

Micromeles DW.CAISNE emend. Kop.~2cE (Rosaceae, Maloideae) is shown to be generically dis t inct from Sorbus L. emend. CRANTZ. Problems in the t axonomy of the genus are reviewed. The genus appears to he most closely related to Raphiolepis L1NDL, but is readily distinguished by a constant set of characters. Both genera m a y be derived from Sorbus L. emend. CI~ANTZ subg. Aria PER$. Analysis of morphological characters is provided. A survey for flavonoids revealed the presence of vi texin and]or luteolin 7-O-glucoside in some members of the genus in a pat tern similar to t h a t found in certain Asian species of Sorbus. There are also brief taxonomle notes on some of the species which were examined.

I N T R O D U C T I O N

Micromeles DEC~SNE emend. KOEH~E is an Asian genus in the Maloideae (Rosa- ceae). I t contains around 25 species of shrubs and trees distributed from Nepal to the South Kuriles and extending as far south as the Malay Peninsula and Sumatra. The main concentration and possibly the evolutionary centre of the genus as well lies in SW. China and adjacent Burma. The major i ty of the species are confined to the mountains; some extend up to 4,000 m a l t . in the HimMayas. The most widely distri- buted species are M. alni/olia (SIEB. et ZUCO.) KOI~HNE and M. corymbi/era (MIQ.) ](Tm,KM.; the others are more or less localized. The pomes of Micromeles are edible and severM species, such as M. alni/olia (SrE~. et Zvcc.) KOEHt~E, M. japonica (DEcAIS~E) KOI~HNE and M. FoOneri C. K. SCHNEIDER are cult ivated as ornamentals.

Folia Geobot. Phytotax., Praha, 16:181-193. 1981

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182 F O L I A G E O B O T A ~ I C A . E T P H Y T O T A X O N O ~ [ I C A , 16, 1981

Morphologically, the genus is dis t inguished by i ts deciduous, simple, serrate or shallowly lobate leaves, flowers in corymbs, d imerous to pentamerous gynoec ium with styles coalescent at least at base, inferior ovary, deciduous upper pa r t of the h y p a n t h i u m and frui t with membraneous cndocarp a nd dis t inct annu la r cicatricc at the apex. Thus circumscribed, Micromeles DECAISNE emend. KO]~HNE differs clearly from the genus Sorbus L. emend. CRANTZ with which it is of ten merged. I n the past , members of the genus have been var ious ly combined also with other genera in the Maloideae, such as Crataegu8 L., Mespflus L., Pyrus L. or even Photinia LI~DL., and in m a n y herbar ia it is still necessary to sort out vir tual ly all mater ia l of the Maloideae, to get the sheets of Micromeles together .

This review is in tended to draw a t t en t ion to the problems in the t a x o n o m y of the genus.

H I S T O R Y OF THE GENUS

Micromeles is one of the numerous genera in the ~laloideae whose recognition we owe to DECAISNE (1874). He diagnosed it in detail, recognizing five species, all described as new from the Himalayas: M. verrucosa DEeAISNE, M. ca~'tanei/olia DEeAISN~, ~I. rhamnoides DECAISNE, M. kha~iana DECAISN~ and M. Crri/fithii DECAIS~E. Surprisingly, three more species, M. japonica (DEcAISNE) KOE~E, 2}1. alni]olia (SIE~. et Zucc.) KOE~NE (originally described as belonging to Crataegus L.) and M. tiliae/olia (DEcAIs~-E) KOEn~E, clearly belonging to the genus Micromeles as defined by DECAISNE, w e r e referred by him to the genus Aria HosT, now usually included in Sorbus. This obvious error was corrected by KOEHNE (1890) who transferred these species to Micromeles and demonstrated that, on the morphology of reproductive organs, Micromeles is distinct from all other genera in the Maloideae. Alas, KOEHNE'S work has never become generally known, so that doubts as to DECAIS~E'S taxonomic intention continued, even though the genus Micromeles, as circumscribed by KoE~-~E, was adopted by HEDLUND (1901) and SC~NEIDE~ (1906) who both supplied additional distinguishing characters. Revising SE. Asian Maloideae, REHDE~ (1915) concluded that no distinction could be found between DECAIS~E'S genera Aria and Micromeles and submerged the latter as a section into Sorbus, while Aria had been included in that genus by FRITSCH (1898-- 1899). In the absence of a modern monograph of the subfamily, this treatment has been followed by most subsequent authors (see e.g. HA~DEL-MAzZETTI 1933, Yi) et Kux~ 1963, OawI 1965, GAB~IELJA~," 1978). Exceptions include POJ~KOVA (1939) who adopted the genus in the Flora of USSR, and K~LK~AX (1973) who advocated its generic status in .a review of the Malesian Maloideae. DECAIS~E'S treatment is admittedly inconsistent but this objection does not apply to the genera Micromeles and Aria as conceived by KOEHNE. Here, as will be demonstrated further below, the deciduous upper part of the hypanthium combined with an inferior ovary constitutes a distinct dividing line which cannot be ignored.

MOt~PHOLOGICAL C O N S I D E R A T I O N S

In teres t ingly , two dis t inc t types of leaf vena t ion occur wi thin Micromeles. Straight la teral veins ending in the tee th or leaf lobes (eraspedodromous venat ion, Fig. 1, A) are found throughout the subfami ly Maloideae a nd in most species of Micromeles. The other type, with curving veins dissolving a t a dis tance from the leaf marg in (camptodromous venat ion, Fig. 1, B), is characterist ic of the SE. Asian genera Raphio- lepis LINDL. and Photi~ia LINDL. and of the N. Amer ican Aronia PEas. which are all qui te d is t inc t from Micromeles (the first two having evergreen leaves). I t is most surpr is ing therefore to find tha t both types of vena t ion occur in the genus Micro- meles. I t was apparen t ly the craspedodromous vena t i on t ha t made DEC~JSN~ exc]ude

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K O V A N D A A ~ D ( ' t t A L L I ( ' E : T H E G E N U S M I ( ' R O M E L E S 183

M. japonica, M. alni/olia, and M. tiliac/olia froin his Micromeles. Straight veins are usually fewer in number and tend to be correlated with leaves doubly serrate to lobu- late and globose fruit with granulate pulp, whereas species with curving veins usually have leaves simply serrate aatd ovoid or ellipsoid fruit with soft pulp. These correlations are not very well marked, however, and many intermediates occur. I t is questionable therefore whether a subdivision of the genus based solely on the leaf venation would be useful.

�9 "J cm" '

Fig. 1. Leaves: A, M. ~d~i]olia (~I[EB. et Zucc.) KOEHNE; B, M. aronioides (REHDER) ]~.OVANDt. e t C H A L L I C E .

Flower and fruit morphology of Micromeles combirms both primitive and advan- ced characters - - a situation not uncommon in the Malofdeae. The original penta- merous gynoecium has survived in M. caloneura STAPF (Fig. 2, A) but in most species the number of carpels varies from 2 to 3, similarly as in Sen'bus subg. Aria PERS. Regardless of the number of carpels, the styles are always fused at least in their basal parts. The degree of fusion is fairly constant for each species. All members of the genus have an inferior ovary. Contrary to the common belief, this is not character- istic of the subfanfily as a whole, the majori ty of genera having the ovary semi- inferior. Typical inferior ovary is found, besides Micromeles, only in the genera Cra- taegus L., Pyrus L., Malus MILL., Aronia PERS., Cydonia MILL., Peraphyllum NUTT., Raphiolepis LIN])L. and in one of the five subgencra of Sorbus L. era. CRANTZ, Tormin- aria (DC.) C. KOCH (see KO~lZNE 1890, KOVANDA 1961, 1965).

The deciduons calyx requires some comment. I t emerges in various genera of the Maloideae, at different evolutionary levels and associated with a var iety of other characters. While it is diagnostic in one genus, it may be subject even to intra- specific variation in the other. Therefore its value us a t&xonomic character is different in different situations, a fact which even monographers have failed to appreciate. Care should be taken to distinguish between deciduous (partly or totally) calyx teeth and deciduous calyx (or, rather, deciduous upper par t of the floral cup).

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For instance, in Sorbus subg. Torminaria (DC.) C. KOCH it is only calyx teeth that die and are shed after florescence, while the remainder of the hypanthium becomes fleshy and continues as an inseparable part of the fruit. All other subgenera of Sorbus have calyx teeth persistent or even pulpous in fruit. A degree of variation is known to occur in some Caucasian members of Sorbus subg. Aria P]ms. The mar- cescence and falling off of the upper par t of the hypanthium is typical of the genera Micromeles DECAISNE emend. KOEH=~E and Raphiolepis LINDL. Here, the whole portion of the floral cup overtopping the ovary withers and is severed immediately after florescence, leaving a distinct cicatrice on the fruit (Fig. 3, A, B). No deviations have been observed, contrasting with Pyrus L., where the behaviour of the calyx is rather variable (see CHALLIC~. et WESTW0OD 1973) and differences may occasionally be found even within one species (DosT~LEK 1979). I t follows that for Micromeles and Raphiolepis the deciduous "calyx" is an important distinguishing feature.

Fig. 2. L o n g i t u d i n a l sect ions o f flowers: A, M. ca!oneura STAPF; B, M. aronioides (I~EHDEa) KOVANDA et CHALLICE.

SUBDIVISION OF THE GENUS

The taxonomic subdivision of the genus presents serious problems. With floral morphology uniform throughout the genus (except for the number of carpels and the degree to which the styles are coalesced), the infrageneric taxonomy is largely dependent upon vegetative features, combined with a few characters of the fruit.

DECAISNE (1874) did no t d i s t i ngu i sh a n y infragener ic u n i t s a n d ne i ther did KOEHNE (1890). REHDER (1915) saw a ma j o r d i s j unc t i on in t he serra t ion a n d v e n a t i o n o f leaves, p resence or absence o f lent icels on t he f ru i t a n d s t r u c t u r e of t he pulp. Based on these charac ters , he refer red t h e SE. As i an species of his sec t ion Micromeles k n o w n a t t h a t t i m e to two g roups , b o t h u n n a m e d and w i t h no defini te t a x o n o m i c r a n k :

1. Leaves s imp ly serrate , w i t h cu rv i ng veins, f ru i t subglobose , u sua l l y lent icel late , w i t h g r a n u l a t e flesh (M. granulosa, M. verrucosa, ~I. Keissleri, M. polycarpa, M. aronioides);

2. Leaves doub ly serrate , w i t h s t r a i g h t veins, f ru i t ovoid, w i t h sof t flesh (M. japonica, M. alni]olia, M. Hem.~leyi, M. Folgneri).

M. meliosmi]olia and ~I. caloneura whi ch are a b e r r a n t in e i ther g roup , h a v i n g t h e leaves o f t h e second a n d t he f ru i t o f t h e first, were left unclassif ied.

I n a review of t h e Chinese Rosaceae (Yti et K u ~ 1963), Yi3 recognized four series in Micromeles, based on i n d u m e n t u m and v e n a t i o n o f leaves, shape o f f ru i t a n d presence of lenticels:

ser. Alni/oliae: Leaves g lab rous or h a i r y in t h e axi ls on t h e unde r s ide , ve ins s t r a igh t , f ru i t subglobose or ellipsoid, s m o o t h or lent icel la te (M. alni]olia, M. caloneura, M. rh~mnoides, M. meliosmi/olia);

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ser. Thomsonianae: Leaves glabrous or hairy in the axils on the underside, veins slightly curving, fruit globose or ovoid, smooth or lenticellate (M. granulosa, M. globosa, AI. Thomsonii, M. aronioi~es, M. Keissleri);

ser. Folgnerianae: Leaves white-tomentose beneath, veins straight, fruit ellipsoid or subglobose, lenticellate (M. Folgneri, M. Hemsleyi);

ser. Ferrugineae: Leaves mostly ferrugineous-tomentose beneath, veins curving or straight, fruit subglobose or ovoid, smooth or lenticellate (M. r~tbiginosa, M. a~tateria, M. ]erruginea, M. epidendron).

5ram

Fig. 3. Fruits: A, M. alni]olia (Smm et Zucc.) KOEHNE; B, 2~/. aronioides (RE~D~R) KOVANDA et CHALLICEo

I t will be noticed that this system follows essentially REHDER (1915), either of his major groups being subdivided into two, one with leaves more or less glabrous, the other with leaves tomentose. The shape of the fruit and the presence of the lenti- cels are almost useless as serial characters. I t is also evident that the series partly over- lap, making the position of some species doubtful. On the other hand, most extra- Chinese species, such as M. japonica (DEcAIS~E) KOEHN~, may be classified without difficulty.

GABRIELJAN (1978) elevated Y0's series to the rank of subsections within R~H- DER'S section Micromeles of the genus Sorbus.

CHEMOTAXONOMIC SURVEY

A survey of flavonoids in the European members of the genus Sorbus L. em. C~ANTZ (CH~LLICE et KOVA:NDA 1978) revealed that within the pr imary sexual species, vitexin (apigenin 8-C-glucoside) is restricted to S. torminalis (L.) CRANTZ and S. chamaen~espilus (L.) CRA~TZ, both of which represent separate subgenera, Torminaria and Chamaemespilus respectively. Five different flavone O-glycosides, luteolin 7-O-rhamnosylglucoside (FT), luteolin 7-O-diglucoside (FV), luteolin 7-O-glucosidc (F2), luteolin 4'-O-glucoside (F4A) and apigenin 7-O-glucoside (F3) were found to be restricted to S. tormi'nalis (L.) CRA~TZ alone, of the primary sexual species. The European representatives of the subgenera Aria PERS., Cormus (SPAcH) D~CgARTRE and Sorb~s s. str. were found to lack both flavone C- and O-glycosides.

However, an extension of this survey into the Asian representatives of Sorbus and Micromeles (CgxLLICE et KOVANDA 1981) has revealed that vitexin and/or

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186 FOLIA GFOBOTANICA ET PHYTOTAXONO~IICA, 16, 1981

the five flavone O-glycosides axe present in some nmmbers of the subgenera Sorbus s. str. and Aria. PE~S. I t is thus evident that some of the Asian representatives of Sorbus s. str. and Aria PEas. have retained chemical ancestral characteristics whilst the migration of these subgenera into Europe was accompanied by the loss of both vitexin and flavone O-glycosides. The survey also revealed that vitexin and/or luteolin 7-O-glucoside are present in some members of the genus Micromeles. Table 1 sunmlarizes the occurrence of these flavonoids. Care was taken to see that each of YiY's series was represented at least by one species.

I t is of interest that the series Alni/oliae appears to lack completely both vitexin and luteolin 7-O-glucoside. In the series Thomsonianae, both of these flavonoid types occur, but they tend not to co-occur in the same specimen; it is surprising that there is so much variation between specimens of the same species. The series Folg- nerianae seems to contain vitexin only, but of the three specimens of M. Folgneri C. K. SCHnEIDEr, only one contains vitexin. The series Ferrugineae contains both flavonoid types but with intraspecific variation in M. epidcndron (HAI~D.-MAzz.) KOVANDA et CHALICE and the absence of both flavonoid types in M. /errugi~ea. With the general prevalence of intraspecific variation it would not be surprising if, for instance, examination of further specimens of M./err.uginea (WE~zm) KOEH~E revealed the presence of either or both of the two flavonoid fypes in this species. F rom the flavonoid data it would appear that within Micromeles, the series Ab~i- /oliae represents the most cvolutionarily advanced group within the genus, because it is this group alone which seems to have completely lost both flavonoid types.

Full details of the paper chromatographic methods for the detection of flavone C- and O-glycosides in herbarium leaf extracts are given in CHALHCE (1974) and CrIALLICE et KOVA~DA (1978).

RELATIONSHIPS TO OTHER GENERA

In the Maloideae, phyletic relationships are often obscured by the phenomena of convergent and parallel evolution, resulting in varied and sometimes contra- dictory generic delimitations. Even with this in ufind it is still possible to speculate on the affinities of the genus Micromeles which is one of the most remarkable mem- bers of the subfamily. By its membraneous endocarp, Micrmneles is referred, together with Sorbus L. era. Can~-TZ, Pyrus L., Malus MILL. , Aroni(~ PEAS., Cydonia MILL., Docynia DECA/SNE, Photinia LI~TDL., Eriobotrya LINDL., Raphiolepis LINDL., Stran- vaesia LINDL., Amelar~chier MED., Per(Iphyllum NUTT. and C&lenomeles LINDL. to the tr ibe Sorbeae. This, and the other tribe, Crataegeae, are perhaps the only natural groupings within Maloideae above the rank of genus.

Within the Sorbeae, the nlost obvious affinity is the small genus Raphiolepis LISDL. which differs from Micromeles by its evergreen leaves, flowers in racemes or panicles, constantly dimerous gynoecium, thick seed and embryo with thick cotyledons (see KALKMAN 1973). Unfortunately the limited chemotaxonomic data available (Cr[ALLICE 1973, 1974) is of no help here: Raphiolepis LINDL. does not appear to contain flavone C- or O- glycosides, or any other phenolics of chemosys- tematic interest, which might indicate relationship with any other genus of the Ma- loideae. The genus Raphiolepis LINDL. includes but a few species found in SE. and

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K O V A ~ ' D A A N D C H A L L I C E : T H E G E N U S M I C R O M E L E S 187

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190 F ( ) L I A G E O B O T A N I C A E T P H Y T O T A X O N O ~ I C A , 16, 1981

E. Asia (from S. China and Thailand to Japan, Philippines and Borneo), thus con- stituting a natural extension of the range of Micromeles.

~elationships of Micromeles to the genus Sorbus are less apparent. Only the sub- genera Aria PE~s. and Chamaemespilus (DC.) C. KOCH can be considered. Morpho- logically, it is not inlpossible to derive Micromeles from Sorbus subg. Aria. Some Himalayan species of Aria come close to Micromeles, having an almost inferior ovary and styles fused at base. However, in the Himalayan Aria these characters are never associated with the deciduous calyx. This is occasionally found only in the Caucasian endemics Sorbus s~fusca (LEDEB.) BOISS., S. caucasica ZINSERL. and S. ha]astana GABn. which obviously belong to another evolutionary stock. Chemi- cally, the derivation of Micromeles fronl Aria is feasible. The same may be said of the subgenus Chamaemespffus in which the carpels are fused nearly to the top of the ovary cells and the ovary is ahnost completely sunk in the hypanthium. In view of its small European range, however, it is impossible for C/~amaemespilus to be linked up with Micromeles. Fused styles are found in the monotypic European and W. Asian subgenus Tormi~mria (DO.) C. Koch which however is quite distinct on other morphological characters (see KOVANDA 1961, CHALLICE or. KOVANDA 1978). The remaining two subgenera of Sorbus, subg. Cormus (SPAcH) DUCHXRTRE and Sorbus s. str., are immediately eliminated front these considerations on account of their pinnate leaves which are now generally thought to be derived from simple leaw, s.

The small N. American genus Aronia PERS., which is sometimes merged with Sorbus, has leaves with eamptodromous venation, flowers h~ corymbs, pentamerous gynoecimn with styles fused at base, semi-inferior ovary and persistent, calyx. Phytogeographically, it is also to be excluded from this discussion.

I t can therefore be postulated, as a working hypothesis, that the genera Micro- meles and Raphiolepis originated from a common ancestor, probably Aria-like, in the mountains of SW. China, thus representing parallel phyletic lines.

The flavonoid data, taken alone, does not serve to differentiate Micromeles fronl Sorbu8 as a whole. Certainly the rather restricted range of flavonoids in Micromeles, relative to some Sorbus species, indicates that Micromeles is of a more recent phylo- genetic age. This is working on the assumption that as evolution progresses, various flavonoids are lost by sequential loss-mutations. I t is unfortunate that Micromeles and Sorbus do not possess such clear-cut chenlotaxononlic characters as Pyrus (arbutin) and Malus and Docynia (dihydrochaleoncs) which serve to delineate these genera so unambigously as monophyletie entities within the 3laloideae (see CHM, LICE 1973, 1974).

NOTES ON THE SPECIES EXAMINED

Micromeles alnifolia (SI~B. et Zucc.) K o E H ~ Gatt. Pore. 21, 1890

(Fig. 1, A; 3, A)

This arboreseent species is by far the most widely distributed member of the genus, ranging from North and Central China to the South Kuriles, Japan, Taiwan and Korea (for a distribution map, see HORIKAWA 1972). The material for the chemical analysis was chosen to cover different parts of the distribution area but despite the

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KOVANDA A~'D CHALLICE: THE GENUS ~[IUIt~O~IELES 191

wide range of morphological variation, no differences in the presence or absence of flavonoid constituents could be detected. In the material examined, the number of carpels varied front 2 to 4. Aria tiliae]olia DECnJS~E, thought to be synonymous with M. alni/olia (SIEB. et Zrcc.) KOERNE by t~EHDER (1915) and GABRIELJAN (1978) is perhaps best t reated as a variety or subspecies (cf. SCHNEIDER 1906).

Micromeles caloneura STAPF Kew .Bull. Misc. Inf. 1910: 192, 1910

(Fig. 2, A)

A tree related to M. alni]olia (SIEB. et Zucc.) KOEHNE, from which it is readily distinguished by its elliptic-oblong leaves with 10--12 pairs of veins and pyriform fruit. The indumentum of the leaves varies considerably and speeimenr with leaves densely pubescent beneath could well be placed in ser. Folgnerianae. An interesting feature is the pentamerous gvnoecium which is however not diagnostic as flowers with three or four carpels also occur. The styles are coalesced in the lower third.

Micromeles meliosmifolia (I~ERDE~) KOVA~-DA et CHnL~ICE, comb. nova

B~t.~.: Sorb~l.; me!io.~'mi]oli~z I~EHDER in SARGENT P1. V~ils. 2: 270, 1915.

This is another arboreseent species, referred by REHDER tO the relationship of M. Scl~werinii 0. K. SCHNEIDER and M. caloneura STAFF. From the latter it differs by the ovate to elliptic-ovate leaves with 18--24 pairs of veins, shorter petioles and subglobose fruit.

Micromeles aronioides (REHDER) KOVANDA et CHALLICE, comb. nova

B~s.: Sorbus aronioides I~EHDER in SARGENT P1. Wils. 2: 268, 1915.

(Fig. 1, B; 2, B)

A segregate of M. Keis.sleri C. K. SCRNEIDER from which it is separated by its glabrous inflorescence, ovoid fruits (subglobos~ in M. Keissleri), longer petioles (about 1 cm long, contrasting with 0.5 cm in M. Keissleri), and narrower, finely serrate leaves. Specinmn K14 is from one of the three collections upon which REHDER'S original description is based.

Micromeles corymbifera (MIQ.) K.~LK~N Blumea 21: 437, 1973

As demonstrated by K~J~KMAN (1973), M. corymbi]era (MIQ.) K~LKMAN is the correct name for what has been known as Micromeles qranulosa (BERTOL.) C. K. SCHNEII)ER or Sorbus granulosa (BERTOL.) I%EHDER. Unlike plants from the northern part of the range, material from Malaya and Sumatra usually has leaves and in-

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192 FOLIA GEOBOTANICA ET PHYTOTAXONOIV[ICA, 26, 1981

florescences completely glabrous but there is much intergradatio~ and a clear sepa- ration is not possible, even at the varietal level (see KALKMAN 1.e.). I t is interesting to note, however, that all three Malesian specimens (K28, BM5, K29) contained vitexin but the other did not.

Micromeles epidendron (HANDEL-MAzZETTI) KOVANDA et CHALLICE, comb. nova

Bas.: Sorbus epidendro~ HANDEL-MAZZETTI Ariz. Akad. ~,Viss. Wien, Math.-Nat. KI., 60: 135, 1924.

(Fig. 3, B)

A species resembling M./erruginea (WENzm)KoEH~E but differring by its coar- sely serrate leaves (finely and remotely serrate in M./erruginea) and many-flowered, dense inflorescence (few-flowered and thin in M./erruginea). The ferrugineous in- dumentum of the leaves and infloresccnces varies considerably.

Acknowledgements

We are grateful to the Curators of the herbaria BM, E, K, PR and PRC for their kind permission to remove portions of their herbarium materiil for chemical analysis. Thanks are also due to the British Council and the Czechoslovak Academy of Sciences for financing travel between Czechoslovakia and the United Kingdom.

SUMMARY

Micromeles DECAIS~]~ emend. KOEH~E is an Asian genus irt the Maloideae dis- tinguished by the deciduous, simple, serrate or shallowly lobate leaves, flowers in corymbs, dimerous to pentamerous gynoecium with styles coalescent at least at base, inferior ovary, deciduous upper part of the hypanthium and fruit with membra- neous endocarp and distinct annular cicatrice at the apex. Its generic status is substantiated by morphological and phytogeographical evidence. Analysis of mor- phological characters was carried out, revealing various combinations of both primitive and advanced characters. A survey for flavonoids covering 11 species of Micromeles demonstrated that vitexin and/or luteolin 7-O-glucoside are present in some members of the genus. Their pattern is similar to that found in certain Asian species of Sorbus. The rather restricted range of flavonoids indicates that Micromeles is of a more recent phylogenetie age. Its relationships to other genera are discussed. The genus appears most closely related to Raphiolepis LINDL. from which it differs by its deciduous leaves, flowers in corymbs, dimerous to pentamerous gynoeeium, flat seed and embryo with thin cotyledons. Of the genus Sorbus, the most obvious affinity is the subgenus Aria, PERS. I t is suggested that Micromeles and Raphiolepis originated from a common ancestor, probably Aria-like, thus representing parallel phyletic lines. There are brief taxonomic notes on Micromeles alni/olia (SIEB. et Zucc.) KO:EHNE, M. caloneura STAPF, M. meliosmi/olia (I~EHDER) KOVANDA et CHALLICE, M. aronioides (Rm~DER) KOVANDA et CHALLICE, M. corymbi/era (MIQ.) KALKMAN and M. epidendron (HANDEL-MAZZETTI) KOVANDA et CtIALLICE.

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KOVANDA AND CHALLICE: THE GES~US I~IICRO~IELES 193

LITERATURE CITED

C~ALLICE J . S. (1973): Phenol ic c o m p o u n d s o f t h e s u b f a m i l y P o m o i d e a e : a e h e m o t a x o n o m i c su rvey . -- P h y t o e h e m i s t r y , Oxford, 12: 1095--1101.

CHALLICE J . S. (1974): l { o s a c e a e c h e m o t a x o n o m y a n d t h e origins o f t h e P o m o i d e a e . - - Bot . Jou rn . L inn . Soc., L ondon , 69: 239--259.

CHALLICE J . et KOVANDA M. (1978): F l avono ids as m a r k e r s of t a x o n o m i c re la t ionsh ips in t h e genus S o r b u s in Europe . - - Presl ia, P raha , 50: 305- -320 .

C~ALLICE J. et KOVANDA M. (1981): C h e m o t a x o n o m i c s u r v e y o f t he genera S o r b u s a n d M i c r o m e l e s in Asia. -- Not . R oy . Bot . Gard. E d i n b u r g h (in t h e press).

CHALL~CE J . S. et WESTWOOD M. N. (1973): N n m e r i c a l t a x o n o m i c s tud ies of t h e g e n u s P y r u s us ing b o t h chemica l and bo t an i ca l charac ters . - - Bot . Jou rn . Linn . Sot . , L o n d o n , 67: 121-- 148.

D~:CAlS~E J. (1874): M6moire sur la famille des Pomac6es . -- Nouv . Arch ives Mus. His t . Na t . , Paris , 10: 131--192.

DOSTg_LEK J . (1979): J s o u n a ,'lzeml ~eskos lovenska re l ik tn i hruhn~ ( P y r u s ) ze sekce P a s h i a ? - - Preslia, P raha , 51: 203- -211 .

F~ITSCH K. (1898--1899) : Zur S y s t e m a t i k der G a t t u n g S o r b u s . - - Oesterr . Bot . Z., Wien , 48: 1 - -4 , 47- -49 , 167- -171 ; 49: 381--385, 426- -429 .

GAI3RIELJA~ E. C. (1978): R j a b i n y ( S o r b u s L.) Zapadno j Azii i Gimalaev . -- E r e v a n . HXNDgL-MAzZ~,T~I H. yON (1933): Symbolae s inicae: bo tan i sche Ergebn i sse der Exped i t i on

der A k a d e m i e der W i s s e n s c h a f t e n in W i en n a c h Si idwest -China , 1914--1918, VI I . -- Wien . H~Dr.UND T. (1901): Monograph ie der G a t t u n g S o r b u s . - - Kongl . S v e n s k a V e t e n s k a p s a k a d .

Hand l . , S tockholm, 35/1: 1-- 147. I~ORIKAWA Y. (1972): A t l a s o f t h e J a p a n e s e flora. - - Tokyo . K_ALXMAN C. (1973): T h e Males ian species o f t h e s u b f a m i l y M a l o i ' d e a e ( R o s a c e a e ) . - - Blmnea ,

Leiden, 21: 413- -442 . KOEHI~E E. (1890): Die G a t t u n g e n der Pomaceen . -- Wissenschaf t l i che Beilage z u m P r o g r a m m

des F a l k - R e a l g y m n a s i u m s zu Berlin. -- Berl in. KOV~TDA M. (1961): F lower a n d f ru i t m o r p h o l o g y of S o r b u s in corre la t ion to t h e t a x o n o m y

of t h e genus . - - Presl ia , P r a h a , 33: 1 - -16 . KOVANDA M. (1965): On t h e gener ic concepts in t h e M a l o i d e a e . - - Preslia, P r a h a , 37: 27 - -34 . O~w~ J. (1965): F lora o f J a p a n . - - W a s h i n g t o n D.C. POJAaKOVA A. I. (1939): R o d 729. -- Melkoplodnik - - M i c r o m e l e s DEceit . - - I n : F lora SSSR

IX , Moskva et L e n i n g r a d , p. 406--407. RE~DE]~ A. (1915): R o s a c e a e . Subfam. P o m o i d e a e . - - I n : S.~QE~T C.S.: P l a n t a o Wi l son ianae 2.

Pub l i ca t ions o f t h e Arno l d A r b o r e t u m , C a m b r i d g e (Mass.), no. 4: 263- -345 . SCHNEIDER C. K . (1906): I l lus t r ie r tes H a n d b u c h der L a u b h o l z k u n d e L - - Jona . Yi) T. T. e t KUAN K . C. (1963): T a x a nova R o s a c e a r u m s in icorum (1). - - A c t a P h y t o t a x . Sin.,

Peking , 8: 214- -236 .

Rece ived 6 March 1980