Illustrations of Indian Botany, Vol. 1/Combretaceae

by Robert Wight

LX.— COMBRETACEAE.

This is one of the most strictly tropical orders we have yet had to examine, for, though some species extend beyond these limits yet none go beyond the warmer latitudes on either side.

The species are all either trees or shrubs, often scandent, sometimes with opposite, sometimes alternate, coriaceous, simple, undivided, exstipulate leaves, rarely with pellucid dots. The flowers are regular, generally bi-sexual, but sometimes by abortion, unisexual, or polygamous, arranged in axillary or terminal spikes or capitulse.

"Calyx 4-5 lobed, lobes deciduous. Petals alternate with the lobes, or wanting. Stamens twice as many as the lobes, rarely, equal in number to them or thrice as many : filaments distinct, subulate : anthers bi-locular, bursting longitudinally. Ovarium coherent with the tube of the calyx, 1-celled : ovules 2-5, pendulous from the apex of the cavity : style 1, slender : stigma simple. Fruit drupaceous, baccate, or nutlike, 1-celled, indehiscent, often winged. Seed solitary (by abortion) pendulous. Albumen none. Radicle superior : cotyledons usually leafy, and either convolute or variously folded, sometimes fleshy and plano-convex.—Trees or shrubs. Leaves alternate or opposite, exstipulate."

Affinities. These are not easily defined according to DeCandolle, the polypetalous genera approach Myrtaceae while the apetalous ones have a closer affinity with Santalaceae and Elaeagneae, and even with Laurineae through Gyrocarpus. Combretum differs from the rest of the order in having quaternary flowers with 8 stamens, and folded not spirally convolute cotyledons. From Myrtaceae and Onagrarieae and Memecyleae, they differ in their 1-celled ovary and pendulous ovules. From Santalaceae and Elaeagneae they are distinguished by the foliaceous convolute or plaited, not fleshy cotyledons. This last structure, which separates them from all other orders, allies them with Gyrocarpeae which has spirally convolute cotyledons, but from which they are easily distinguished by the longitudinal, not valvular, dehiscence of the cells of the anthers. "The solitary carpel of which the fruit consists is peculiar to these and to Alangieae, and neatly distinguishes those two orders from all others of the myrtal alliance" Lind. Upon the whole the weight of authority is in favour of the present station as all those writers who have given much of their attention to natural affinities agree in placing Combretaceae among the series of orders with which they are here associated.

Geographical Distribution. As indicated above this is strictly a tropical order and is found within the tropics of Asia, Africa, and America, but not in New Holland. Some of the Indian species however extend considerably beyond the 23° of northern latitude and are even found as far north as the foot of the Himalayas, several are found in the Malayan peninsula and in the Eastern Islands. In the Indian peninsula, though only 9 genera and 19 species are des- cribed, the order may be said to abound as most of the species are of frequent occurrence. Those of Terminalia and Conocarpus abound in the alpine tracts, while Comb' etum and Getonia are equally abundant on the plains in those parts of the country where they do occur. Combretum, of the two, is more generally diffused. Getonia is principally confined to the western coast and about Courtallum, but not limited to these localities.

Properties and Uses. Most of the species of Terminalia are strongly astringpnt and the bark of several may be used for tanning. The leaf galls and fruit of T. chebula are much used by dyers as a mordant for fixing their colours, as well as for imparting, with alum, a durable yellow dye, and with a ferruginous earth an excellent black — Ainslie. The galls are used for making ink, the bark for tanning, they are also employed in medicine when astringents are required, and in short, on all occasion-- whether in the arts or medicine, where astringents are necessary the bark or fruit or galls of Terminalia or Myiobalanus may be used. Nearly all the species of Terminalia and Conocarpus are large timber trees and some of them yield very useful timbar, but I do not find any precise accounts of their respective qualities. Terminalia (Pen- taptera) coriacea or perhaps T. glabra " has a trunk straight and lofiy ; wood of considerable diameter, so as to be made into solid wheels for buffalo carts ; strong, hard and heavy" — Berry in Roxb. Fl. Ind. This tree is not mentioned by Ainslie. No useful property is assigned to any of the scandent forms but the wood of Lumnitzera racemosa (Petaloma alternifolia, Roxb.) is said to be remarkably strong and durable. The plant is however rare in this part of India and so far as I am aware does not attain a sufficient size to be of much value. Vast quantities of it are daily carried from the Sunderbunds to Calcutta for fuel.

Remarks on Genera and Species. This order is divided info two tribes Terminaliae and Cornbreteae. The former distinguished by its spirally convolute cotyledons and by the petals frequently wanting: in the latter the cotyledons are either thick plano-convex or irregularly and longitudinally plaited, sometimes they are thin and foliaceous or intricately folded. Of the former of these tribes most of the genera are essentially characterized by their flowers, in Ter- minalia the calyx is 5-cleft, the limb small, deciduous, petals none : in Getonia I lie limb of the calyx is large and persistent. From these Poivrea and Lumnitzera are distinguished by having petals; the former being separated from the latter by its deciduous, not persisrent, limb of the calyx ; and more readily by its habit, which is twining and a native of inland districts while the latter is erect, arboreous, and a native of salt marshes on the const along with ihe Rhizophovae. Conocarpus is readily distinguished from the rest of the order by its capitate apetalons flowers, compressed ovaries and flattened, almost winged, closely imbricating seed ; somewhat resem- bling a pine cone in miniature whence the name. The Indian species of this genus are all trees natives of alpine districts though rarely found on the highest hills. Poivrea is a twining shrub resembling Combretum, but separated by its quinary flowers and 10 stamens, not quaternary with 8 stamens, the fruit in both is winged. By far the most conspicuous member of the order on account of the profusion and magnificence of its flowers is the so called Rangoon creeper ( Quisqualis indica J now so deservedly a favourite in Madras gardens.

Some recent writers the principal of whom are Lamark and DeCandolle has proposed to divide Teiminalia into 4 genera, taking the characters from the fruit. Terminalia is by them restricted to those species with flattened drupes the margins of which are sometimes extended into wings or much attenuated. Those with rounded or obscurely furrowed often fleshy drupes have received from Lamark the name of Myiobalanus — a third set characterized by having 5-7, longitudinally, winged fruit, Roxburgh has called Pentaptera : while a fourth with 3-5 angled fruit the angles extending into unequal sized wings have received of the name Chuncoa (Gimbernantia, Ru. & Pav.) both of which genera are adopted by DeCandolle, but he unites Myrobalanus and Terminalia . The Peninsular flora presents species appertaining to each of these forms.

Conocarpus has in like manner been by Dr. Wallich divided into two genera and apparently on good grounds, namely, the direction of the carpels and the comparative length of the calyx. He limits Conocarpus to the American species the tube of the calyx of which is not produced beyond the ovary, and the carpels are retrosely imbricated, not winged : while of the Indian species, which have the calyx produced considerably beyond the ovary and contracted into a slender neck, with the carpels imbricated upwards, winged and crowned by the neck of the calyx he forms the genus Anogelssua, from DeCandolle's section of the same name. This innovation is not adopted by Meisner in his genera Plantarum though it has been in the flora Senegambiae.

EXPLANATION OF PLATE 91.

1. Terminalia Belerica, (Roxb.) Flowering branch — natural size.

2. A tio'vcr, the limb of the calyx to show the inser- tion of the stamens.

3. An anther afier dehiscence.

4. A fruit full grown.

5 6. The same cut transversely and vertically.

7. A seed with the cord, by which it is suspended from i lie apex of the cell of the nut.

.8. The testa removed to show the cotvledons.

y. Cut transversely, to show the cotyltdons spirally convolute.

EXPLANATION OF PLATE 92.

1 . Quisqualis indica — natural size.

2. The ovary and the tube of the calyx opened, to show the insertion of the stamens and its adhesion with the lower portion of the style, the extremity only of the latter being free.

3. Stamens.

4. Ovary cut transversely, 1 -eel led.

5. Cut. vertically, showing three pendulous ovules.

6. Stigma.

7. A full grown fruit.

8-9. The same cut transversely and vertically. 10. The kernel removed from the cell.

COMBRETACEÆ.

TERMINALIA BELERICA. (ROXB.)

COMBRETACEÆ.

QUISQUALIS INDICA. (Linn.)