Page:Illustrations of Indian Botany, Vol. 2.djvu/403

ILLUSTRATIONS OF INDIAN BOTANY.

209 Tribe IV. Borkage^e. Ovary consisting of 2 two-celled or separable carpels; Style central baselar, springing from the gynobase. Fruit 2-4-parted, of 2 two-celled or 2-partible carpels. Seed exalbuminous. — Shrubs or herbs. This last is divided into 6 subtribes, sometimes differing from each other nearly as much as the tribes do among themselves. These I deem it unnecessary to introduce, there being so few Indian species referable to this tribe.

De Candolle briefly remarks of these, "an order approaching Labiates and Verbenacece by the structure of its fruit, and Solanacece and Hydrophyllaceos by its flowers." Lindley remarks of Cordiacece, "The plaited cotyledons and dichotomous style first led to the separation of this order from Borrageworts, with which it was formerly associated, chiefly it is to be supposed, on account of the roughness of the leaves. Von Martins remarks that it is in fact much nearer Convolvulacece, from which it differs in its inverted embryo and drupaceous fruit. It seems to me impossible to admit Cordiacece even into the same category as Borragece, the indispensable pecularities of which are gyrate inflorescence and nucamenta- ceous fruit, neither of which circumstances occurs here. 1,1

With respect to the last two circumstances mentioned, the first, the inflorescence, is nearly met here in the decided tendency towards gyration observable in the accompanying species of Cordia, and the cotyledons are but very slightly plaited, thus showing so far a strong leaning towards Ehretiaceos in both these points, but differing in the twice dichotomous style, and ascending not pendulous ovules: but the ovary is the same in both, a more important character than one derived from the mature fruit.

In regard to Ehretiaceos, Lindley remarks, "a branch of the old Borraginece distinguished by a terminal style, proceeding from the apex of a perfectly concrete ovary of 4 cells, a baccate fruit, and seeds furnished with thin fleshy albumen. The order is recombined with Borraginece by Alph. De Candolle, but it seems sufficiently characterized by its concrete carpels, and the presence of a small quantity of albumen. The separate not separable nuts of Borraginece are so peculiar, notwithstanding Cerenthe has them combined in pairs, that a real objection seems to exist to the disregard of so good a mark by the combination with them of these concrete-fruited Ehretiads/'

Under his order Ehretiaceos Lindley ranges De Candolle's 2nd and 3rd tribes. There is no doubt a considerable difference between them and Borragece, in the ovary and fruit, and espe- cially in the hypogynous origin of the style of the latter, but in other respects we find much affinity and a progressive transition. Between Cordia and Ehretia the greatest difference I find is in the position of the ovules, ascending in the one, pendulous in the other. The seed, too, dif- fers, being exalbuminous in the former, and more or less copiously albuminous in the latter. The only other distinction of ordinal value between the two is the twice divided stigma of Cordia and the simply cleft one of Ehretia, but that is neutralized by Tournefortia (a genus of Ehre- tiacece) in which it is entire. The different position of the ovule is not alone sufficient to con- stitute an ordinal character, and neither, I apprehend, ought so much importance to be attached to the circumstance of the 4 carpels cohering into a single nut in one, and continuing distinct in the other. The transition, from Ehretiaceos through Tournefortia to Heliotropecs, seems easy, though the latter differs nearly as much from the former as Ehretiece does from Cor- dieos ; hence if Heliotropium and Ehretia may be united as members of one family, there seems but little reason for separating Cordia and Ehretia.

The passage from Heliotropecs to Borragece is not quite so smooth as in the preceding examples ; the difference in the ovary and fruit, and especially in the hypogynous insertion of the style of the latter being greater. But on the other hand the similarity of habit is more marked and of a kind, for the most part, so conspicuous as to lead even a cursory observer to detect the relationship. It therefore becomes a question of some nicety to decide, whether relationships easily detected by external characters is to give place to others deduced from microscopic research ? which those indicated above certainly are. My impression is that the verdict will be in favour of the former ; and to that extent, confirmatory of De Candolle's views in this instance.