Illustrations of Indian Botany, Vol. 1/Tamariscineae
XIX.-TAMARISCINEAE.
This is a small order, composed of very ramous shrubs, or small trees ; with ex-stipulate, scattered, simple, entire, sessile, minute leaves ; sometimes, in Tamarix, scale-like, closely embracing the stem, and lapping over each other, like tiles (imbricating.) The flowers are regular, hermaphrodite, generally ranged in terminal racemes or spikes; pedicels furnished with a small bractea.
The calyx is free or slightly adherent at the base, persistent, of 5 sepals, imbricated in oestivation. The torus is either obsolete, or expanded into a small disk, glanduliferous on the margin. The petals equal the number of the sepals, and are alternate with them, inferior, sometimes adherent at the base, and marcescent, or withering without falling off. The stamens are hypogynous, equalling, or double, the number of the petals, rarely, by abortion, fewer than in this proportion, (this I have observed in Trichaurus ericoides,) occasionally monadelphous at the base; the anthers 2-celled, opening longitudinally. The ovary is sessile, l-celled, usually
with three, many-ovuled, placentae, either attached to the base, or extending some distance along the valves; in the latter case they are occasionally dilated, so as to form a 3-celled fruit. Stigmas usually three, either sessile or supported on a style, simple, dilated, or plumose. Capsule 3-valved, 1-celled, seed numerous, oblong, beaked, with a tuft of down at the apex, sometimes villous all over. Albumen wanting, or according to Bartling sometimes present, and then thin fleshy or mealy. Embryo straight, the radicle pointing to the hilum.
Affinities. The place that this order should occupy in the natural system has long been a subject of dispute among Botanists, some, among whom Jussieu set the example, placing it among the orders with perigynous stamens, that is, having the filaments inserted into the calyx, in this arrangement he has been followed by DeCandolle and others. More recently a different view of their structure has been taken, and is now generally adopted, according to which, the stamens are considered hypogynous, that is inserted into the torus or receptacle, but the true place of the petals, whether hypogynous or perigynous, seems still doubtful. This transition though in itself of Tittle moment, has the effect of materially altering the place of the order in the linear series of Jussieu's arrangement by transferring it from a class with perigynous to one with hypogynous, stamens. This part of the natural method being constructed on artificial principles, that is, simply according to the insertion of the stamens, whether into the torus or into the calyx, (a distinction in such cases as the present more easily made upon paper than found in nature) has the effect of occasionally widely separating orders in other respects very nearly allied. By assigning a perigynous in place of a hypogynous, insertion to the stamens of Tamariscineae would have the effect of bringing them among a different set of orders : and in place of standing between Polygaleae and Elatineae in the Peninsular flora, as they now do, they should, on the supposition of the stamens being perigynous, have been placed near Paronychiaceae and Portulaceae. Dr. Lindley, sensible that associations based on niceties of structure so little appreciable by the senses as that upon which these classes are made to rest are almost useless in practice, has availed himself of habit and some other peculiarities of structure to assist in fixing their proper place in the vegetable system, and owing to the similarity of foliation, considers it more advisable to keep this order "near Illecebreae, with which it accords in its unilocular syncarpous often 3-valved fruit, and scale-like leaves." Amidst these conflicting views I confess, though comparatively slightly acquainted with the natural system, I prefer leaving it in its present place, not on account of its hypogynous stamens and petals, since these seem not so easily made out, but on account of its parietal placentation, loculicidal dehiscence, and exalbuminous seed (in which respect it quite accords with the orders between which it is placed) these points of structure, affording marks of distinction most easily made out under all circumstances, and not liable to be mistaken in any. According to this view, the order would have been better placed, it appears to me in Dr. Lindley's 3 group (Parietosae) of Polypetalae, in his "Alliances of plants" than in the one (Syncarposae) in which it now stands.
Essential Character. Polypetalous : stamens fewer than 20 : ovary wholly superior; carpels of the ovary combined into a solid pistil : sepals imbricated, more than 2 : stamens hypogynous : seeds comose (furnished with a tuft of down) leaves without stipules.
Geographical Distribution. The few species of this order are exclusively confined to the northern hemisphere of the old world, but are widely distributed over it. Their most frequent station is on the sea coast and on the banks of rivers. In India they seem to prefer banks in the sandy beds of streams, which are dry the greater part of the year, in such situations I have repeatedly found them. They seem however to have met with but little attention among the natives of this part of the country as I have not been able to discover any Tamul name for them.
Properties and Uses. The bark of some of the species is slightly bitter and astringent, and probably tonic. Rhazes assigns to it diuretic, aperient, and cooling properties. In Denmark the branches are used in place of yeast for making beer, and the decoction of the leaves and young shoots is prescribed as a substitute for guaiac. The ashes of Tamarix gallica and Africana growing near the sea are remarkable for containing a quantity of sulphate of soda! and cannot be used as a ley for washing, as they coagulate the soap, while those growing in sweet soil in the interior are free from it. From a species or possibly a variety of T. Gallica, which grows about Mount Sinai, there exudes a kind of manna, (from the punctures of an insect which perforates its bark) which has received the name of "Manna of Mount Sinai," and has by some travellers, fancifully enough been supposed the Manna of the Scriptures. Some of the species produce abundance of galls. In Egypt the Tamarix Orientalis produces them of a deep red colour, and are much used in dyeing. All the species of this country are said by Mr. Royle to produce galls, having the properties of oak galls, but I have not been able to discover whether they are ever gathered in this part of India. It seems probable from an observation of Mr. Royle, that the galls imported into India from Mooltan, are chiefly of the Tamarix, not Oak galls, and that it is with them our bazars are principally supplied, on which account we would do well to examine the tamarix jungles, which often extend along the beds of our rivers for miles together, to ascertain to what extent they could supply our wants.
Remarks on Genera and Species. Three of the four genera referred to this order are found in India, the fourth, (Bronnia) which seems but a doubtful member,is from America. It has been referred by Kunth to Portulaceae, but is placed in this order by Dr. Lindley. The genus Trichaurus is certainly very nearly allied to Tamarix, but sufficiently distinguished by its decandrous flowers, its cup-shaped torus bearing the stamens on its margin, and by the different form of the styles and stigmas. The beak of the seeds, which seems to form so excellent a distinguishing mark between it and Tamarix, appears to differ rather in degree than in kind, when examined under a high magnifier, since both show the beak, but in Trichaurus it is very conspicuous under the most ordinary magnifier, and even to the naked eye, while the other requires one of high powers to bring it out as represented in the figure. The dissected flower of Trichaurus is not perhaps the most suitable that might have been selected, since it seems evidently defective, in so far as having only 8 in place of 10 stamens, which last in the absence of positive evidence to the contrary, must on account of the pentasepalous calyx and 5-petaled corolla, be looked upon as the normal number. But that this is merely an irregularity, perhaps of a single flower, is rendered further probable by the circumstance of there being only 2 in place of 3 styles, three being the normal number of the order.
This figure as exhibiting a departure from the usual and regular form is not without its use, since it explains the cause of one of the greatest obstacles to the perfecting of the Linnean sexual system, depending as it does on a single set of organs, the tendency namely, of different flowers, even on the same stalk, to vary in the number of stamens and pistils, and thereby, to indicate very different places in the system for the plant to which they may belong. When our distinctive marks are taken from the relative position and number of all the different parts of the flower to each other, the formation of the ovary, and position of the ovules, added to the general habit of the plants, we have so many points of comparison, that the chances of our being misled through variations or imperfections^ in any one set of organs, are greatly diminished. Doubtless sufficient uncertainties still exist in the natural method to lead different Botanists to form different opinions both as to the situation orders ought to occupy in the series, and sometimes, in nearly allied orders as to the genera that should be respectively referred to them ; but yet, in spite of these drawbacks, its advantages over any artificial arrangement, and the Linnean is certainly the best, are such, as to ensure its general adoption by all who would study botany as a science, and not as a mere means of discovering the name of a plant, as he would the meaning of a word in a dictionary. But even this, in tropical botany, is often a very difficult operation when attempted with no other assistance than that afforded by the Sexual System, because among tropical plants, the sexual organs are so very liable to vary in number from unions among themselves, or from suppressions and additions of parts, giving rise to innumerable instances of irregular forms, among plants usually ranged in classes with regular flowers : even the Papaw, one of the most constant of dioecious plants; I have seen with regular bi-sexual flowers.
But to return from this digression, it appears that the genus Trichaurus is amply distinguished from Tamarix by having double the number of stamens that it has sepals, and by having the filaments attached to a distinct hypogynous disk, independent of the more distinct beak of the seeds.
The only species of the genus is, I believe, abundant on the dry banks in the bed of the Palar river below Wallajabad.
EXPLANATION OF PLATE 24.
A. 1. Tamarix gallica var Indica. Natural size. 2. Flower opened, showing the imbricated sepals, the petals, stamens, superior ovary, styles, and dilated stigmas. 3. A stamen showing the sagittate form of the anthers. 4. A single flower as it appears on being removed from the branch, the exterior pointed sepal-like leaf in front, the Bractea. 5. Ovary cut transversely, and opened, showing the parietal attachment of the ovules to the base of the carpels. 6. A mature fruit after dehiscence. 7. A seed with its downy tuft. All more or less magnified.
B. 1. Flower of Trichaurus ericoides. 2. Sepals opened, and the petals removed, to show the insertion of the stamens and ovary. 3. A stamen, anther pointed, 4. A seed with its beak. All magnified.
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A. TAMARIX GALLICA. B. TRICHAURUS ERICOIDES.