If, as M. de Candolle considers, the leaf and the branch differ merely in the fact that the vascular system is complete in the latter, and partly atrophied in the former, it would surely be better to consider the "calyx-tube" of the rose as a concave axis rather than as a leaf, seeing that he admits the fibro-vascular system to be complete in the case of the rose.
With reference to this point the reader is referred to Mr. Bentham's account of the morphology and homologies of the Myrtaceæ in the 'Journal of the Linnean Society,' vol. x, p. 105. See also ante, pp. 71, 77.
Some doubts also exist as to the nature of the beak or columella of such fruits as those of Geraniaceæ, Malvaceæ, Umbelliferæ, Euphorbiaceæ, &c. The nature of the organ in question may probably be different in the several orders named; at any rate the subject cannot be discussed in this place, and it is mentioned here because, now and then, it happens that the organ in question is completely wanting, and hence affords an illustration of suppression.
FOOTNOTES:
[464] 'Théorie de la feuille.' p. 24.
CHAPTER II.
SUPPRESSION OF FOLIAR ORGANS.
This subject may be considered, according as the separate leaves of the stem or of the flower are affected, and according as either the number of members of distinct whorls, or that of the whorls themselves, is diminished.
The terms aphylly, meiophylly, and meiotaxy may be employed, according as the individual leaves are altogether wanting, or with reference to the diminished number of parts in a whorl, or a decrease in the verticils.
Aphylly.—Entire suppression of the leaves is a rare phenomenon. Under ordinary circumstances it occurs in most Cactaceæ, in some of the succulent Euphorbias, and other similar plants, where the epidermal layers of the stem fulfil the functions of leaves. But even in these plants leaf-like organs are present in some stage or another of the plant's life.