. Botany of the living plant. Botany. THE CARPEL AND OVULE 255 seen in the Lily (Fig. 199). Such fusion of carpels, with or without their sinking into the receptacle, has developed progressively, and has appeared repeatedly in distinct evolutionary lines. The result is the solid and massive gynocciuni, whether with superior or inferior ovary. A transverse section of the inferior ovary may still show evidence of its carpellary origin almost as clearly as in the superior ovary. This is seen in Iris, where notwithstanding that the carpels are sunk in the receptacle, their struc- ture, and even th
. Botany of the living plant. Botany. THE CARPEL AND OVULE 255 seen in the Lily (Fig. 199). Such fusion of carpels, with or without their sinking into the receptacle, has developed progressively, and has appeared repeatedly in distinct evolutionary lines. The result is the solid and massive gynocciuni, whether with superior or inferior ovary. A transverse section of the inferior ovary may still show evidence of its carpellary origin almost as clearly as in the superior ovary. This is seen in Iris, where notwithstanding that the carpels are sunk in the receptacle, their struc- ture, and even the arrangement of the chief vascular strands resembles in some degree that seen in the superior ovary of the Lily (Fig. 203). The conclusion follows that in such cases the gynoecium is still to be referred in origin to foliar structure, more or less completely fused with or sunk into the tissue of the receptacle. The structure of the carpel, where it is distinctly leaf-Hke, as it is in the pod of fig. 203. ^ , . , Transverse section of the inferior the rea, corresponds in essentials to that ovary of IHs. compare the snjxrinr ^ r ,. 1 r u *- • vc A A ovary of Lily, Fig. 201. F. O. B. of a fohage leaf, but simplified. A vas- cular strand usually traverses each margin, as in Caltha (Fig. 200). This is related to the fact that the ovules are seated there; or, as it is described, the placeyitation is margiyial. It is probable that this was the regular primitive position for ovules. But sometimes they appear scattered over the inner surface of the carpellary wall, as in the Flowering Rush (Butomus), the Poppy, or the Water-Lily. This is described as superficial placentation, and it probably originated by the spread of the ovules to the surface. Sometimes they appear as though seated on a prolongation of the axis into the ovarian cavity, as in the Pinks and Primroses (Appendix A). This i:. called free-central placentation, and it also is probably derived from the marginal type, by br
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