178 ORGANOGRAPHY. BOOK I. 



necessarily originate in the margins of the carpellary leaf : and 

 hence they have been compared to the buds found upon the 

 margins of some true leaves, and may be shown to be actually 

 analogous to them in structure. 



Of the truth of this there can now be little doubt; for, to 

 say nothing of such plants as Bryophyllum, which habitually 

 form buds on the margins of the leaves, or of Malaxis 

 paludosa, in which the edge of the leaf is frosted by little 

 miscroscopical points, that are neither exactly ovules nor 

 exactly buds, or of the bracts of Marcgraavia, which Tur- 

 pin, with much ingenuity, has endeavoured by mere argu- 

 mentation to prove analogous to the primine of the 

 ovule, it has been shown by Henslow that in the Mignio- 

 nette the ovules do actually become transformed into leaves, 

 either solitary or rolled together round an axis, of which the 

 nucleus is the termination. {Camhr. Phil. Trans, vol. v. 

 part i.) Engelman also mentions and figures instances of 

 similar changes ; but he does not say in what plants, nor are 

 his figures by any means satisfactory. He, however, conckides 

 from the observations of himself and Schimper, that " the 

 ovules are buds of a higher order, their integuments leaves, and 

 their stalk the axis, all which in cases of retrograde metamor- 

 phosis are converted into stem and gi-een leaves." {De An- 

 tholysi prodromus, § 44. 76. t. 5. f. 4, 5.) I should rather say 

 that the evidence goes to prove that the ovule is a leaf-bud in 

 a particular state, that the integuments are scales {i. e. rudi- 

 mentary leaves) rolled up and united at their touching mar- 

 gins, and that the nucleus is the growing point, to which I 

 have already on so many different occasions directed attention. 



In almost all cases the o\'ule is enclosed within an ovary, 

 as would necessarily happen in consequence of the convolute 

 nature of the carpellary leaves : but if the convolution is im- 

 perfect, as in Reseda, the ovules are partially naked ; and if 

 it does not exist at all, as in Cycadeae and Coniferae, the 

 ovules are then entirely naked, and, instead of being fertilised 

 by matter conveyed through the stigma and the style, as 

 in other plants, are exposed to the direct influence of the 

 pollen. This was first noticed by Brown; and, although since 

 contradicted, seems to be j)erfect]y true. 



