REVIEW OF THE GENUS SOLENA ( CUCURBITACEAE )

The genus Solena Lour. is redefined, and its 3 species and 1 subspecies are keyed out and described: S. amplexicaulis occurs in S India, S. heterophylla, with 2 subspecies is widespread, but does not occur in S India, and S. umbellata (Klein ex Willd.) W.J. de Wilde & Duyfjes, comb. nov., occurs in S India and Sri Lanka. The status of S. heterophylla subsp. napaulensis (Ser.) W.J. de Wilde & Duyfjes, comb. & stat. nov. needs further study as this subspecies is very similar to the more widespread subsp. heterophylla, but it is distinct by sigmoid thecae. Solena amplexicaulis is taxonomically more distinct from the other two species of Solena. In southern India Kedrostis foetidissima much resembles Solena in general habit, especially by the more or less amplexicaul leaves, and therefore it is discussed and keyed out against Solena.


INTRODUCTION
In the past the genus Solena Lour. was regarded to consist of only one widespread variable species, S. amplexicaulis (Lam.) Gandhi, ranging from NE Afghanistan through India and Sri Lanka, eastward to eastern and southern China, and into West Malesia (Jeffrey, 1980b). However, for China (Wu, 1984;Lu & Zhang, 1986;Chen, 1995) a second species, S. delavayi (Cogn.) C.Y. Wu, was accepted. Examining Solena over its whole area we found that 3 species can be recognised: 1) S. amplexicaulis in S India; 2) S. umbellata in S India and Sri Lanka; and 3) S. heterophylla with two subspecies: subsp. heterophylla, variable in general appearance and widely distributed from NE Afghanistan eastward, and subsp. napaulensis (synonym S. delavayi) in the area of N India, east to China. The latter occurs in mountainous areas; it is likewise variable in general habit and very similar to the type subspecies, but distinct by its obvious sigmoid thecae. According to the above cited Chinese authors, S. delavayi is further distinct by being monoecious and by having deeply 5-lobed (not 3-lobed or subentire) leaves, but we doubt whether these additional characters hold true unambiguously. The remaining three Solena taxa have straight or curved, never S-shaped, thecae. As the two character states for the thecae, straight or curved versus sigmoid, is a strong argument in the distinction of genera in Cucurbitaceae, it is surprising that, because of the absence of additional characters, one has to admit both character states within one single species S. heterophylla. For the sake of convenience we accept the plants with sigmoid thecae as a separate subspecies, subsp. napaulensis. This means that within the genus Solena, apparently as a unique exception, species occur with straight and curved thecae, as well as with sigmoid thecae. A comparable exception of a strong genus character, variable within one genus, viz. stamens free versus stamens connate, is known in Neoalsomitra (De Wilde & Duyfjes, 2003).
Members of the genus Solena are easily recognised in the field by their comparatively short petioles, with the blade more or less embracing the stem. In southern India and Sri Lanka this character has led to incidental confusion of sterile S. amplexicaulis and S. umbellata with Kedrostis foetidissima (synonym K. rostrata); all three species superficially look very much alike, because of short-petioled leaves. Furthermore, Kedrostis foetidissima and S. amplexicaulis both have rather similar beaked fruits. Therefore, K. foetidissima is included in the key to the species. The genus Kedrostis contains several species in Madagascar and Africa and two species in Asia. The Asian species of Kedrostis are distinct from Solena e.g. in the male flowers by short filaments, inserted in the throat of the receptacle-tube, by the connective produced beyond the anther-thecae, and the apparent absence of a disc (as it is adnate to the receptacle-tube).
Asian Kedrostis can also be confounded with Corallocarpus, which differs in having anthers without produced connective, and with fruit opening in an operculate manner, with a ring-shaped seam at base. The fruits of most Kedrostis and of Solena are indehiscent. The petioles of Corallocarpus and Kedrostis (except K. foetidissima) are comparatively long.
Solena is characterised by basally inserted stamens, and a conspicuous glabrous or hairy disc, which is sometimes cup-shaped and deeply lobed, but mostly consists of thickish strap-shaped lobes, at the base of the receptacle-tube in both sexes. These lobes are not to be regarded as pistillode or staminodes, because in female flowers they are present around the base of the style, beside the slightly higher-up inserted small staminodes. In male flowers they are inserted between the stamens and there is no central remnant of a style. Solena Lour. (1790) 514;Keraudren (1975)  Herbaceous or at base subwoody climbers, 2-6 m tall, with perennial rootstock or tubers; monoecious or dioecious. Leaves simple, extremely variable in shape; petiole short, rendering the leaves frequently semi-amplexicaul, and with the basal lobes often overlapping. Tendrils simple. Probract minute, linear, often caducous or absent. Flowers white or cream coloured. Male flowers in sessile or peduncled condensed racemes. Pedicels suberect, persistent, often with bracts at base or inserted about halfway. Receptacle-tube cup-shaped. Sepals 5, minute. Petals 5, free, valvate-induplicate, small, hairy. Stamens 3, two 2-thecous, one 1-thecous. Filaments free, long, inserted at base of the receptacle-tube. Anthers without or with swollen connective, not produced beyond the anther-thecae; thecae either erect and straight, or oblique and (slightly) curved, or sigmoid. Disc 3-(or 4-)lobed, conspicuous, carnose. Female flowers single, solitary or at base of male raceme; perianth resembling male. Ovary narrowly ellipsoid, glabrous or hairy; ovules few or rather many. Staminodes 3 (or 4), inserted on the receptacle. Disc a deeply lobed cup or consisting of 3(-5) lobes, at base of style. Fruit fleshy, glabrous, hairy or scabrous. Seeds few or rather many, little compressed or nearly globose.
Distribution -S India; possibly not in Sri Lanka.
Habitat & Ecology -In bushes and thickets, over shrubs; altitude 0-800 m. Flowering and fruiting: May to January.
Notes -1. Solena amplexicaulis resembles vegetatively the other 2 species of Solena and Kedrostis foetidissima, and also Adenia wightiana (Passifloraceae). Sterile as well as flowering and fruiting specimens of S. amplexicaulis may be confused also with Kedrostis foetidissima (see introduction and key to the species).

Solena heterophylla Lour.
Distribution -Two subspecies. Widely distributed, from NE Afghanistan, the Himalayas, through Northern India to S & E China, and SE to Myanmar, Thailand, Indochina, Peninsular Malaysia and Java; not in Sumatra, Borneo.
Habitat & Ecology -Prefers a seasonal climate, often in open ± deciduous forest, pine savannah; on granitic as well as on calcareous soils; 0-3300 m altitude. Flowering: March to November; fruiting: April to November.
Notes -1. The forms according to leaf shape, as proposed by Cogniaux (1916), and repeated by Keraudren (1975) have no taxonomic value, although Smitinand on a field label (Thailand) stated that deeply narrow-lobed leaf forms are found in the mountains.
Habitat & Ecology -As the species, but apparently not occurring above 2000 m altitude.
Note -A deviating male specimen, Duthie 21434, from Pilhibit District, W Himalaya, c. 2000 m altitude, differs from all other specimens by having 1 or 2 long-pedicelled male inflorescences from each node, with many-flowered racemes provided with persistent, relatively large glandular bracts. In general habit it resembles subsp. napaulensis, but the specimen is male (not monoecious) and the thecae (in bud) are curved, not sigmoid. Plant monoecious (or dioecious?), shoots often prostrate. Leaves subentire to deeply spreadingly 5-lobed, the middle lobe much longer. Inflorescences either male, with flowers fascicled in a sessile, or a short-peduncled raceme, usually with a co-axillary  Male flowers: as in subsp. heterophylla, but thecae vertical and sigmoid, not forming a nearly closed ring. Female flowers: pedicel 10-25 mm long; ovary hairy, mostly with few or many, glabrous glossy blackish spots. Fruit (broadly) ellipsoid, 3-3.5 by 2-2.5 cm, scabrous-hairy or subglabrous, base and apex ± rounded; fruiting pedicel 20-40 mm long. Seeds c. 7 by 6-6.5 by 3-3.5 mm, grey-brown, smooth, not bordered. Distribution -N India, Nepal, S China (Yunnan), Myanmar.
Notes -1. The status of S. heterophylla subsp. napaulensis as a subspecies is unclear because in general habit, vegetatively as well as in most flower details, it is very similar to subsp. heterophylla. However, the strikingly S-shaped thecae and the fruit (according to Cogniaux (1916), for Melothria delavayi smaller, and glabrous) distinguish it clearly. More complete material should be studied to ascertain whether the sigmoid thecae is a valid character, or that this character-state may occur occasionally in specimens of local populations within the vast distributional area of S. heterophylla.
2. Specimens from high altitudes in the Himalayas, with 5-lobed leaves, monoecious flowers, the female flowers long-pedicelled, and ovary and fruit having dark dots, are quite distinct. However, several collections, partly from lower areas and often incomplete, look similar but may have characters tending to be intermediate between subsp. napaulensis and subsp. heterophylla; see also note 3. A specimen obviously belonging to subsp. napaulensis but with the thecae only weakly sigmoid is Clarke 28348 (K), from Kashmir.
3. In Chinese literature (Wu, 1984;Lu & Zhang, 1986;Chen, 1995) the present taxon is named Solena delavayi, but we think that this name is synonymous with S. heterophylla subsp. heterophylla. In the original description of Melothria delavayi Cogn. the female flowers are erroneously described as situated solitary in the axil of the male raceme ("solitarii in eadem axilla cum masculis"). The anthers are described as oblong, c. 1 mm long, with ciliate loculi. The S-shape of the thecae is neither indicated in this description nor in the preceding key to the species (Cogniaux, 1916: 80). Moreover, on the lectotype-sheet in P (Delavay 2009, a male plant), Cogniaux made a pencil drawing of an opened male flower, depicting the thecae as only somewhat curved and erect, not S-shaped. In most specimens of subsp. napaulensis that we studied, the anthers with the vertical, sigmoid thecae are c. 2 mm long. Contrary to the statements by Cogniaux (1916: 124) and Jeffrey (1980b: 15), the type material Delavay 2009 consists of different elements, viz. female and male flowering plants: in P male flowering with a loose fruit; in K female flowering and fruiting, and with some loose fruits in an envelope. The male material in P is chosen as lectotype. Creeper or climber, to 3 m, subglabrous; dioecious; roots tuberous. Leaves ovate or narrowly elliptic, 4-14(-20) by 2-10 cm, entire or deeply hastately 3-lobed, adaxially finely scabrous, abaxially with scattered minute gland-hairs, base cordate, apex acute or obtuse, margin remotely dentate; petiole 4-11 mm long. Probract absent. Male inflorescences subsessile or to 7 mm long peduncled, condensed, few-or many-flowered sub-umbellate racemes up to 1 cm long. Male flowers: pedicel 2-8 mm long, articulate at apex; bracts carnose, ± terete, (narrowly-)ellipsoid, 1-2 mm long, apiculate, without glands, inserted on upper half of the pedicel, (sub)persistent; corolla and anthers very much the same as in S. heterophylla, except for glands on petals: receptacle-tube 3-5 by 2-4 mm; sepals triangular, 0.1-0.2 mm long, wide apart; petals triangular, 1-1.2 mm long, with simple papillose hairs and with numerous minute gland-hairs; filaments 2.5-4 mm long, glabrous, inserted at or slightly above the base of the receptacle-tube; anthers subglobose, c. 1.5 mm diam., connective broad, convex, with gland-hairs; thecae curved, forming an oblique or horizontal nearly closed ring; disc lobes 3, coarsely hairy and with scattered gland-hairs, c. 1 mm long. Female flowers similar to those of S. heterophylla: pedicel 5-10 mm long; ovary glabrous. Fruit solitary at the node, (narrowly-)ellipsoid, 3-7 by 1.5-3 cm, at both ends attenuate (acute, not narrowed into a beak), glabrous, smooth, slightly angled; when dry yellowish, with c. 9 faint ribs, when ripe red; fruiting pedicel 10-12(-15) mm long. Seeds 10-20, subcircular in outline, 6.5-7.5 by 5-6.5 by 3-5 mm, the faces light (grey-)brown, and with a broad paler, finely corky-warted and cracked marginal belt, rendering the seed base somewhat emarginate. Distribution -S India, Sri Lanka.
Notes -1. Willdenow (1805) presents a number of references to previous authors, the first being "Bryonia umbellata. Klein in litt.". Our present species is represented in B-W by two collections: one unnumbered collection by Roxburgh, and one collection by Klein, annotated: "765 Bryonia sp. nov. …… Nandaradah". The latter sheet, with the smaller leaves, has been chosen as lectotype. In K there are two sheets of the Rottler herbarium (Herb. Rottlerianum), one sheet with 3, the other sheet with 8 separately labelled different collections, all representing the present S. umbellata. Among these collections obviously isotype material is present, but the precise assignment of which fragment is an isolectotype needs further consideration.