. Botany of the living plant. Botany. THE CARPEL AND OVULE -55 seen in tlic Lilj' (Fig. 199). Such fusion of carpels, \\ ith or witiiout their sinking into the receptacle, has developed progressively, and has appeared repeatedly in distinct evolutionary lines. The result is the solid and massive gynoeciunr, 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 ev
. Botany of the living plant. Botany. THE CARPEL AND OVULE -55 seen in tlic Lilj' (Fig. 199). Such fusion of carpels, \\ ith or witiiout their sinking into the receptacle, has developed progressively, and has appeared repeatedly in distinct evolutionary lines. The result is the solid and massive gynoeciunr, 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 Fig. 303. Transverse section of the inferior ovary of Iris. Compare the superior ovary of Lily. Fig. 2or. F. O. R. The structure of the carpel, where it is distinctly leaf-hke, as it is in the pod of the Pea, corresponds in essentials to that of a foliage 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 placentation is marginal. 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 (Biitomus), 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 cavit).-, as in the Pinks and Primroses (Appendix A). This is called free-central placentation, and it also is probably derived from the marginal type, by breaking away the partitions,
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