Illustrations of Indian Botany, Vol. 1/Melastomaceae

by Robert Wight

LXII.—MELASTOMACEAE.

A vast tropical order, containing according to Meisner's list, 100 genera, excluding four of Memecyleae, which he considers a tribe only of Melastomaceae and not a distinct order. This union of these two families is, it appears to me, scarcely authorized by the character of the flowers, and is not supported by the fruit and seed which differ greatly in the two orders. According to DeCandolle's enumeration there are about 800 species, which number, I believe, has been very considerably augmented since the publication of his work. Of that number 620 are from America leaving a comparatively small number for Asia, Africa, and New Holland.

In our Prodromus 1.5 species only are described, a number which my more recent excursions have not materially extended, though they have afforded ample evidence of the difficulty of distinguishing the species of this order, through their tendency to vary their forms. I find for example on comparing many very dissimilar looking specimens, no good marks by which to distinguish them as species. A more intimate acquaintance, however, with growing plants may perhaps furnish us with characters by which to augment the number. In some parts of this

country, and also in Ceylon, they are very abundant, and many of them most magnificent and showy plants.

The species are either trees, shrubs, or herbaceous plants, with opposite, exstipulate, entire leaves ; usually without pellucid dots and marked by three or more thick longitudinal nerves or ribs. The flowers are usually bi-sexual, regular, often panicled, rarely solitary, the panicles or cymes usually contracted. The most remarkable peculiarity of this order is the position of the stamens in aestivation. The filaments are inserted near the orifice of the calyx, and the anthers are bent down into its tube, occupying the vacant space between it and the ovary, after the expansion of the flower they ascend. A somewhat similar arrangement is observable in Memecyleae with this difference, that the ovary is there altogether inferior and the anthers fill the cup of the calyx. The relative position of the ovary in the two orders generally affords a good discriminating mark between them, out is not always to be depended on as some Melastomaceae resemble Memecylon in this respect.

" Calyx with 3-5 teeth or divisions, which are more or less deep, or are sometimes united and separated from the tube like a lid. Petals equal to a segment of the calyx, perigynous, twisted in aestivation. Stamens either equal in number to the petals and alternate with them, or usually twice as many, the alternate ones of a different shape and perhaps never with fertile pollen : filaments in aestivation, bent downwards towards the bottom of the calyx : anthers long, 2-celled, bursting usually by one or two terminal pores, rarely longitudinally. Ovarium with several cells, rarely completely combined with the tube of the calyx, very rarely entirely free from it, usually cohering with it more or less by means of 3-10 longitudinal nerves, thus forming as many cases as the anthers which they contain during aestivation : ovules indefinite : style 1 : stigma simple, entire, capitate or reduced to a mere point. Placentae in the axis. Fruit pluri- locular : either free and then capsular, valvate and loculicide ; or adherent, baecate (a balausta), and indehiscent. Seeds numerous, minute. Albumen none. Embryo straight or curved : radicle pointing to the hilum: cotyledons equal or unequal. — Leaves opposite, undivided, not dotted, 3-9-nerved."

Affinities. My acquaintance with this very extensive order being slight, and my means of extending it very limited, I refrain from attempting to offer any opinion of my own on this head, but that this article may not be, by so much, deficient I shall introduce the whole of the valuable remarks of Dr. Lindley on their affinities for the benefit of those of my readers who may not have an opportunity of consulting the original.

" The family of Melastomaceae"" remarks DeCandolle, in an excellent memoir upon the subject, " although composed entirely of exotic plants, and established at a period when but few species were known, is so well characterized, that no one has ever thought of putting any part of it in any other group, or even introducing into it genera that do not rightly belong to it." These distinct characters are, the opposite leaves, with several great veins or ribs running from the base to the apex, something as in Monocotyledonos plants, and the long beaked anthers; to which peculiarities combined there is nothing to he compared in other families. Permanent, however, as these characters undoubtedly are, yet the cause of no uncertainty having been yet found in fixing the limits of the order, is rather to be attributed to the small number of species that have been examined, than to the want of connecting links : thus Diplogenea has traces of the dots of Mijrtaceae, which were not known to exist in Mdastomaceae until that genus was described; several genera are now described with a superior ovary, a structure which was at one time supposed not to exist in the order ; and, finally, in the remarkable genus Sonerila, the leaves are sometimes not ribbed.

The greatest affinity of Melastomaceae is on the one hand with Lijthraceae, on the other with Mijrtaceae and their allies ; from the former they differ in the aestivation of their calyx not being valvate, from the latter in having the petals twisted before expansion and no dots on the leaves, and from both, and all others to which they can be compared, in their long anthers bent down parallel to the filaments in the flower, and lying in niches between the calyx and ovary; with the exception of Memecylaceae, in which, however, the union between the calyx and ovary is complete, and which have leaves destitute of the lateral ribs that so strongly point out Melastomaceae. The structure of the seeds of Memecylaceae is also different. Geographical Distribution. As stated above, America may justly be considered the head quarters of this tribe, upwards of 600 species having been obtained from that quarter out of about 800 described by DeCandollein his Prodromus. Since the publication of that work many genera and species have been added, whence I believe I under estimated the number of species now known at one thousand. Of this number probably about 100 are natives of continental India and Ceylon ; of these Roxburgh seems only to have known 14, as 7 out of 21 described by him are from Pulo Penang and the Moluccas. Blume has added largely to the list from Java, having probably nearly doubled the Indian list, that is, supposing that the other genera are somewhat in proportion to Medinilla, of which that Island produces 21 species. In Ceylon Mrlastomaceae are also numerous, and several new and very curious species have recently, through the researches of Colonel Walker, been brought to light; among these are several species of Osbeckia, five or six of Sonerila and three or four of Medinilla. One species of this last genus, but differing somewhat from the generic character especially in the anthers being spurred only, not auricled and spurred, at the base, is among the handsomest plants I have ever seen. It is an enormous creeper, adheres firmly to the trees on which it grows, climbs to the tops of the highest trees of the forest, and covers them with a profusion of large crimson flowers. This species T first saw in company with Colonel Walker (in a. dense forest above Ramboddy) to whom I have dedicated this noble plant Medinilla f Walkerii. On the alpine ranges of the southern provinces and in Malabar, I collected many specimens, several of which, I then supposed were new species, but which, on a more careful examination and comparison with others, must I fear be considered as varieties only, at least I have not yet been able to find satisfactory distinctive marks by which to raise them to the rank of species. Figures of some of these shall shortly appear in the Icones. In addition to these from the south, a few species spread northwards and even extend to the foot of the Himalayas, but these are so few in number as scarcely to form an exception to the general rule that this is truly a pre-eminently tropical order.

Properties and Uses. Astringency is said to be the predominating quality of the order, but little seems yet known regarding them. Lindley remarks that the order " though one of the most extensive known is entirely destitute of any unwholesome species. The succulent fruit of many is eatable that of some dyes the mouth black, whence the name Melastoma. It may be here remarked as somewhat curious that the genus established by Burman under this name, for which he is quoted as the authority and of which he figured two species, is not that now called Melastoma, but Osbeckia, the original name being limited to a genus, of which it does not appear he ever saw a single plant.

Remarks on Genera and Species. The Indian genera are few and easily distinguished, I do not therefore think it necessary to devote much space to this division. Osbeckia has either a quaternary or quinary order but the stamens are all alike. Melastoma, which in general appearance it resembles is easily distinguished by the stamens, one-half having the anthers sessile on the apex of the filament, the other having them supported on a long pedicel or stipe, apparently formed from a prolongation downwards of the connectivum : by this mark alone these allied genera can always be distinguished at a glance. Sonerilla is separated from both by its ternary order of parts — Medinilla has a quaternary series, the anthers with auricles and a spur at the base, in M. Walkerii the auricles are wanting, but the spur is considerable, on which account I have marked the genus with a doubt. Among my collection of Mergui plants communicated by Mr. Griffith I find a second species presenting the same peculiarity, agreeing in that respect with Pternandra, but distinguished by the anthers of the latter opening by a longitudinal slit not by a pore as in the other. The genus Triplectrum abounds about Courtallum but seems rarely to flower as I, in the course of several visits to that place, could not find a single plant in flower though I walked over acres of ground covered with the plant. This disappointment I the more regretted, as the genus is founded on a single specimen and that not a very good one, whence I fear it may only be a modified state of Medinilla.

As above remarked I have found but few new species, but have seen great reason to believe that those already described are apt to vary so considerably, as to lead to the supposition of their being distinct when separately examined, though when numerous specimens are compared at the same time, the differences, which in extreme forms might appear so considerable as not to admit of union, are yet found gradually to meet through the medium of intermediate forms. Dr. Arnott in a paper on the Ceylon Metastomacene published in the Companion to the Botanical Magazine has defined several new ones, the abridged differential characters of which J subjoin, though I do not feel quite certain that they are all distinct.

SONERILA.

1. S. Ceylanica; branches glabrous, anthers cordate- ovate, obtuse.

2. S. affinis; branches nearly glabrous, anthers cor- date-oblong, attenuated, slyle .filiform, stigma capitate.

3. S. glaberrima; branches and leaves glabrous, an- thers lanceolate, acuminated, style thickened in the middle, stigma minute.

4. S. hirsutula; stem herbaceous, branches hirsute, petals ovate, acuminated, anthers lanceolate-subulate.

5. S. Wightiana; stem herbaceous, branches hirsute, anthers linear-lanceolate, obtuse, stigma minute.

6. S. Hookeriana; siem somewhat woody, branches clothed with reddish short wool, anthers cordate-ovate, obtuse, stigma capitate.

7. S. robusta; stem somewhat woody, branches cover- ed with close spreading hairs, petals broadly oval, acute, anthers lanceolate-subulate.

OSBECKIA.

Am hers 8.

1. O. Ceylanica; annual, anthers subulate.

2. O. truncata ; branches hirsute, leaves one inch to one inch and a quarter long, anthers truncated.

3. O.parvifolia; branches nearly glabrous, leaves three to four lines long, anthers truncated.

Anthers 10, acuminated. Leaves crowded.

4. O. buxifolia; leaves thick and rigid, closely straited.

Leaves rather distant.

5. 0. rubicunda; leaves on rather lo^g petioles, scales of the ca'ys spreading, reddish, style chivate.

6. O. Wightiana; leaves nearly sessile, scales of the calyx adpressed, yellowish, style clavate.

7. O.virgata; leaves at length nearly glabrous on the upper side, flowers somewhat umbelled, style fili- form.

8. O.aspera; branches strigose, upper side of the leaves copiously covered with adpressed bristles, under hirsute on the nerves, and harshly pubescent between them, flowers somewhat racemose, ?tyle filiform.

9. O. Kleinii; bran dies scabrous or hispid, leaves minutely strigose on both sides, flowers shortly race- mose, style fl iform.

10. O. Walkeri; branches shortly tomentose, flowers terminal, solitary, calycine segments elongated; style filiform.

EXPLANATION OF PLATE 94.

1. Sonerila brunones — natural size. 5. A seed nearly mature.

2. A dissected flower, showing the inferior ovary. 6. A cluster of capsules — natural size.

3. The ovary cut vertically, many-seeded. 7. One of them magnified.

4. Cut transversely, 3-celied, with a triangular central placentae and several rows of ovules in each cell.

EXPLANATION OF PLATE 95.

1. Melastoma malabathricum — natural size.

2. A dissected flower, the tube of the calyx divided and forcibly opened to show the insertion of the petals and stamens and the free ovary.

3. Stamens, the larger one unfortunately imperfectly represented as not showing the downward elongation of the connectivum, the character by which this genus is essentially separated from Osbeckia.

4. The ovary cut vertically.

5. Cut transversely.

6. A young fruit.

7. The same cut transversely, the appearance of the interior somewhat altered by drying. The dissections having been made from dried speciu.ens.

8. A seed.

9. The same cut vertically.

10. The cotyledons and radicle removed from the testa.

MELASTOMACEÆ.

SONERILA BRUNONIS. (W.&A.)

MELASTOMACEÆ.

MELASTOMA MALABATHRICUM. (Linn.)