Page:Illustrations of Indian Botany, Vol. 2.djvu/169

ILLUSTRATIONS OF INDIAN BOTANY-

81 Nevertheless Botanists, in most instances, appear to be against this opinion : I confess I cannot conceive upon what grounds. Usually a material dissimilarity in habit, if accompanied by any clear character, whether of vegetation or fructification, is considered sufficient for the separation of a group of plants into two Orders; in this case the weak, angular stems cause a peculiarity of habit that cannot be mistaken, and the total absence of stipules, to say nothing of the didymous fruit, affords a certain mark of recognition. Surely there is some inconsistency in separating, by the absence of stipules, Caprifoils, which are undistinguishable in habit, while the very same character is rejected when applied to an assemblage of genera all distinctly combined by their habit. The only ground upon which this is intelligible, is that taken by DeCandolle and others, who consider the apparent leaves of Stellates to be in part true leaves and in part leaf-like stipules. To this verbal, but not real distinction, there is this objection, which I conceive quite fatal to it: If a part of the leaves of each whorl in Galium was stipules, the latter must bear a certain proportion to the true leaves ; suppose the whorl to consist of two leaves, each will have two stipules, and consequently the whole number of parts in the whorl must be six, and in all cases the number must be some power of 3. But of the first forty species of Galium, in DeCandolle's Prodromus, only thirteen conform to this rule ; and the frequent tendency in the whorls to vary from 4 to 6, or from 5 to 6, or from 6 to 8, seems to me an incontrovertible proof that the apparent leaves of Stellates are true leaves and not a modification of stipules. To this it may be added, that the admitted leaves are so entirely the same as what M. DeCandolle conceives to be stipules, that no difference whatever can in general be found in their form, colour, anatomy, or degree of development. Such reasons have, however, not proved satisfactory to Botanists, who with one accord appear to range themselves upon the side of M. DeCandolle; and recently the question has been more particularly agitated by one of the most distinguished writers of this country.

Mr. Bentham, in an article on Crusea rubra, published in the Botanist, page 82, after entering at some length and with great skill into a discussion of the arguments employed on both sides of the question, has decided in favour of the opinion of DeCandolle, that a part of the apparent leaves of Stellate plants are stipules. The grounds upon which he has arrived at this conclusion are essentially the following:

1. That the foliaceous organs in Stellates, if viewed as consisting entirely of leaves, do not bear that relation to the angles of the stem which is usual in Dicotyledons; but that the relation becomes apparent if only two of them are taken as leaves and the rest as stipules. (DeCandolle seems influenced by the consideration that it is only two of the apparent leaves which have buds in their axils; but Mr. Bentham does not advert to this.)

2. That in a number of cases, especially in Asperula, two opposite leaves are much larger than the others.

3. That in Spermacoceae and other tribes of Cinchonads, the stipules are connected with the petiole of the leaf into a sheath, and that this sheath exists in Stellates.

4. That the number of parts in each whorl is not necessarily some power of 3, but that, taking two of the parts for leaves, it is immaterial by what number of similar parts those two are separated, because the intermediate processes are analogous to the setae of Spermacoceae, the number of which is variable.

Perhaps this question is more important in appearance than in reality, for in some respects it is a mere difference about words; stipules being rudimentary leaves, and leaves developed stipules. It is, however, connected with some points of speculative interest, especially as regards systematic Botany, and therefore I avail myself of the present opportunity of stating what I conceive to be the objections to Mr. Bentham's line of argument, and why I still retain my original opinion upon the subject.

1. With regard to the relation borne by the leaves to the angles of the stem, it is to be observed, that if those foliaceous organs only which are opposite the angles are said to be leaves in Stellates, and the rest stipules, then we must suppose that Labiate