Below upwards and leaving the placentas with the seeds attached to the replum or framework of the septum.
It was the scene of two naval battles of the t Transverse section of the fruit of the melon (Cucumis melo), showing the placentas (p1), with the seeds attached to them.
The ovary is incompletely divided into many chambers by the ingrowth of the placentas which bear numerous ovules and form in the fruit a many-seeded short capsule opening by small valves below the upper edge.
The ovary of passionflowers is one-celled with three parietal placentas, and bears at the top three styles, each capped by a large button-like stigma.
In many cases, however, the placentas are formations from the axis (axile), and are not connected with the carpellary leaves.
This is seen in cases where the margins of the carpel do not unite, but remain separate, and consequently two placentas are formed in place of one.
Apocarpous, there are generally separ ate placentas at each of their margins.
- Diagrammatic section of a five-carpellary ovary, in which the edges of the carpels, bearing the placentas and ovules o, are not folded inwards.
The placentas are parietal, and the ovules appear sessile on the walls of the ovary.
In these cases the marginal placentas meet in the axis, and unite so as to form a single central one (figs.
In these instances the placentas may be formed at the margin of the united contiguous leaves, so as to appear single, or the margins may not be united, each developing a placenta.
- Diagrammatic section of a five-carpellary ovary, in which the septa (s) proceed inwards for a certain length, bearing the placentas and ovules (o).
In this case the ovary is unilocular, and the placentas are parietal.
- Transverse section of the fruit of the Melon (Cucumis Melo), showing the placentas with the seeds attached to them.
From the centre, processes go to circumference, ending in curved placentas bearing the ovules.
Free central placentation, there fore, has been accounted for in two ways: either by supposing that the placentas in the early state were formed on the margins of 2 FIG.
Carpellary leaves, and that in the progress of development these leaves separated from them, leaving the placentas and ovules free in the centre; or by supposing that the placentas are not marginal but axile formations, produced by an elongation of the axis, and the carpels verticillate leaves, united together around the axis.
At other times they are vertical, as in Datura, where the ovary, in place of being two-celled, becomes four-celled; in Cruciferae, where the prolongation of the placentas forms a vertical partition; in Astragalus and Thespesia, where the dorsal suture is folded inwards; and in Oxytropis, where the ventral suture is folded inwards.