Illustrations of Indian Botany, Vol. 1/Millingtoniaceae

by Robert Wight

XXXVIII.—MILLINGTONIACEAE.

This is a small Indian order limited as yet to a single genus of arborious plants, distinguished by their alternate exstipulate leaves, which are either simple or pinnate, and in the latter case are rendered still more remarkable by their being either abruptly or unequally pinnated. The inflorescence is panicled, the panicles being either terminal or axillary near the summits of the branches. The flowers are small sometimes almost inconspicuous, nearly sessile, on short lateral peduncles of a pale greenish yellow and very numerous.

Sepals 5, persistent, unequal, somewhat in a double series : aestivation imbricative. Petals 5, inserted on the margin of the receptacle, deciduous, alternating with the sepals of two kinds; three outer ones orbicular, entire, with an imbricative aestivation; two interior smaller, acutely bifid, resembling scales. Stamens 5, opposite to the petals, and slightly united to them at the very base ; three exterior sterile, opposite to the larger petals; two interior fertile, opposite to the bifid petals; filaments of the fertile stamens flat : anther, cells globose, dehiscing transversely, placed side by side on the inner side of the saucer-shaped connectivum. Disk, flat, thin, hypogynous, free, except at its point of attachment with the ovary ana receptacle. Ovary ovate, 2-celled; ovules 2 in each cell, superposed. Style simple, short, and thick. Stigma slightly 2 lobed. Fruit a 1-celled, 1-seeded drupe; the dissepiment evanescent above, hardened and persistent at the base. Seed with a small cavity on one side, near the base. Albumen none or extremely thin. Embryo curved : cotyledons thin, foliaceous, folded : radicle curved, pointing to the hilum. Trees. Leaves alternate, without stipules, entire, or rarely pinnated. Inflorescence in panicles, terminal, or axillary near the extremity of the branches. Flowers small, inconspicuous, nearly sessile, on very short peduncles that are arranged along the horizontal branches of the panicles. (W. and A. Prod.)

Affinities. The affinities of this order are viewed in very different lights by different authors. Mr. Arnott and myself aided by a suggestion of Dr. Hooker placed it between Sapindacece and Meliacece. Dr. Lindley looks upon the order as forming but a section or sub-order of Sapindacece, while Meisner for reasons which do not appear refers it to Berberedece, a distribution in which 1 cannot coincide. In confirmation of Dr. Lindley's view it may be stated that my Millingtonia Arnottiana is actually the plant we have described as Sapindus microcarpus, which may be considered a convincing proof of the close relationship existing between them, if not a satisfactory indication that we were premature in separating this genus as the type of a distinct order. However, bringing analogy to bear on the question, we have already seen Hippocratiacece established on its unsymmetrical flowers, and Erythroxylece separated from Malpighiacece on account of the appendages of its petals, hence, if such reasons are applicable to one set of instances they ought to be equally so to another, and as the differences of the arrangement of the flowers between Sapindaceae and Millingloneaceae are certainly equal in amount to those of the other, it must be admitted that if they are to be adopted in the one set they ought equally to be so in the other. In urging this view I do not advocate its adoption, but think with Lindley that the sooner we can retrace a false step the better, and

therefore hope our error should it prove one will be speedily corrected, and at the same time the other to which I have alluded. That the circumstances which induced us to constitute this genus the type of a distinct order may be fairly stated, I shall reprint here, from Jameson's Philosophical Journal, our introductory observations, and also Lindley's remarks explanatory of his views.

"The simple generic character of Millingtonia given by Roxburgh, in his Flora Ind. vol. i. p. 102., although sufficiently exact for the Linnean classification, in which those parts only are accounted stamens that have pollen, conveys little information as to the real structure of parts. The nectarial bodies opposite the petals, are of a very singular shape. The apex (which Roxburgh erroneously represents free) is incurved, and attached in front, similar to the petals of some umbelliferous plants, leaving two large hollows, one on each side, as if for the reception of the cells of an anther. Indeed, their whole appearance is that of abortive stamens, in which light we feel disposed to view them. The bifid scales, at the back of the fertile stamens, are of a very different texture, and these, we believe, are abortive petals. Thus, we have both stamens and petals heteromorphous; the imperfect forms of the one set of organs opposite to the perfect ones of the other. The calyx we have always found to consist of two interior sepals, and three exterior, one of which, and sometimes, but rarely all, are similar in size to the interior, and alternating with them : there are in some species in addition, small close-pressed bracteolae. The mode in which the calyx is placed is well figured by De Candolle (Organ. Veg. t. 37. f. 12. p.) We have, then, a calyx, a corolla, and androecium, each of five parts, placed apparently in a double scries; the one dissimilar to the other, and alternate with it; thus analogically shewing, that the hypogynous disk must be viewed as an outer series of the gymnoecium, the bidentate angles alternating with the two cells of the ovary. At first, also, it would appear that the two outer parts of each organ alternate with the inner of the next, but this is only in appearance; for, if that were the case, the angles of the hypogynous scale would be opposite to the three larger petals, whereas they alternate with them. The real disposition of parts, therefore, will be better understood, if we suppose each organ to be of only one series, and of five parts; the petals alternating with the calyx, the stamens opposite to the petals, and the pistilla alternating with both stamens and petals. That this is the true explanation, is confirmed by the fact, that, in no known plant, where any organ consists of a double series of parts, do the component parts of one series differ in number from those of the other. The asstivation will thus be imbricate and quincuncial; and in such, two or three (as may happen) parts of the same organ are interior. It is. however, remarkable to find them of so very different a structure as occurs in this genus.

The Affinities of Millingtonia have not, so far as we know, been pointed out. The habit is much that of Semecarpus, Mangifera, and Buchanania, and, like the Terebinthaceae, the embryo is campulitropal. The genus Sabia, also, has the stamens opposite the petals, the ovarium bilocular, two ovules in each cell, the one placed above the other; but the petals are likewise opposite to the sepals, and the habit is different: moreover, it is by no means certain that Sabia ought to be referred to the Terebinthaceae; and the characters of all the other genera of the order present little in common with Millingtonia. Our friend Dr. Hooker has suggested an affinity with Sapindaceae; and with different genera of that order, it has several points in common,—as the fleshy disk, the two superposed ovules in each cell, the indehiscent fruit, with part of it abortive; the absence of albumen, and the curved embryo; but that order has usually stamens twice as numerous as the petals, and, in addition, scales or tufts of hair at the base of the petals; so that if, as in Millingtonia, these scales were to be viewed as abortive stamens, the whole number of stamens would much exceed that of the petals. In Sapindaceae, too, the hypogynous disk is fleshy, and is, we believe, the torus : here it is quite free from the receptacle, except at the point of attachment, and appears to be formed by the union of an outer series of styles. Although, therefore, we cannot agree to place it among the true Sapindaceae, we can see but little objection to its forming the type of a new order next them."

The following remarks on the Affinities of this order are extracted from Dr. Lindley's Natural System of Botany. "The plants belonging to this assemblage are looked upon by Wight and Arnott as forming a family distinct from, but closely related to, Sapindaceae. The principal differences pointed out. by those authors are. that in the latter the stamens are usually twice as numerous as the petals, which have scales or tufts of hair at their base; and the hypogynous disk is fleshy. Other points are, indeed, adverted to, but they are either unimportant, or not clearly explained. These authors do not take the same view of the structure of the genus as Roxburgh.

but agree with Jack in considering the number of petals 5. of which three only are petaloid, and the other two bifid and adnate to the base of the two fertile stamens. It appears to me. however, that in reality, in M. simplicifolia at least, there is very great irregularity in the proportion of the parts of the flower; in the calyx I find six pieces, two very minute and external, two larger, but unequal, next the first, and two more, also unequal, in the inside; petals I see only 3, on the face of the largest of which is a distinct trace of a rudimentary scale; the stamens are 5. three of them being deformed, lobed, and opposite to the three petals, the other two fertile alternating with two of the petals, with a membranous tooth on each side at the base (not the apex, as Roxburgh has it), and a remarkable saucer-like connective, on the upper face of which grow two anther-cells, the valves of which are extremely unequal. I do not, therefore, perceive how the genus differs from Sapindaceae, except in the pistil being composed of two carpels in stead of three. But although the number three is what usually prevails in Sapindaceae, yet there are instances of two in Schmidelia, Irina, &c. and of four in Talisia and Dodonaea."

Geographical Distribution. The genus Millingtonia has a wide range though as yet limited to few species. Roxburgh received his specimens from Silhet, of the only two species he knew, since then, I have received specimens from various parts of the Peninsula, Ceylon and Maulmain. Dr. Wallich has also found two, distinct from Roxburgh's, one of which, M. pungens, is found in the Peninsula, M. Arnottiana is a native of the more elevated regions of both Ceylon and the Peninsula, my continental specimens are from the Neilgherries. The leaves in this species are unequally pinnated, which at once distinguishes it from Roxburgh's M. pinnata, which has abruptly pinnated leaves.

Properties and Uses. Nothing is known on this head except that the timber of some of the species is used for various purposes by the natives of the districts where they grow.

Remarks on Genera and Species. Of this order only one genus is yet known, that from which it takes its name. Of the species now 5 in number, Roxburgh knew only two. M. simplicifolia and M. pinnata, to these Dr. Wallich has added M. dillenii folia and M. pungevs, the last M. Arnottiana is now for the first time published under that generic name, and is a native of both the Peninsula and of Ceylon. The characters of two species are already published in our Prodromus, those of the remaining three I shall introduce here with the view of making them better known to Indian Botanists.

MILLINGTONIA. two of them bracteiform; the. exterior petals roundish,

M. dillennfolia, (Wall.) Leaves simple, elliptic, oblong, attenuated at the base, pubescent beneath: the secondary nerves parallel, straight, extending beyond the margin in prickle-like teeth, panicles slender, lax, pubescent ; rachis angled ; flowers somewhat remote on the extreme branches, calyx ebractiate, sepals 5, nearly equal, ciliate on the margin, exterior petals roundish, concave, the interior ones cleft nearly to the base, or half shorter than the petals.

M. pinnata, (Roxb.) Leaves abruptly pinnate, pinnae 6-12 pairs; leaflets elliptieo-lanceolate, glabrous on both sides, denticulate, serrated, the teeth incurved, with the secondary nerves incurved within the margin, confluent; panicles lax, puberulous, rachis angled, sepals unequal, two of them bracteiform : the exterior petals roundish, the interior ones cleft to near the middle equalling the petals.

M. Arnottiana. Leaves unequally pinnate, pinnae 5-7 pairs : leaflets ovate, acuminate, coriaceous, glabrous above, pubescent neneath, quite entire, panicles axillary, large lax and like the periols of the leaves thickly clothed with short rusty colored hairs, rachis terate, sepals somewhat unequal, exterior petals roundish, pointed, interior ones cleft nearly half their length, the points reflexted filaments furnished with two scales below the middle.

Sapendus microcarpus, W. and A. Prod. I. p. 112.

Hab. -- Neilgherriwes and Ceylon.

EXPLANATION OF PLATE 53.

1. Flowering branch of Millingtonia Arnottiana— natural size.

2. A flower partially open.

3. The same dissected.

4. The same, the petals removed, showing the stamens, ovary, &c. in situ.

5. Back and front, views of the stamens and anthers.

6. A diagram of the flower.

7. The ovary cut vertically, showing the ovules superpossed.

8. The same cut transversely,

MILLINGTONIACEÆ

MILLINGTONIA ARNOTTIANA.