382 PARIETAL AND FREE CENTRAL PLACENTAS. [BOOK i. 



such as Corydalis, Viola, and Orchis, the carpels are not 

 folded together at all, but are spread open and united by 

 their edges (fig. 133.) : in that case the placentae do not 

 project at all into the cavity of the ovary, but are still more 

 strictly parietal than the last. 



Jig. 133. 



Another class of anomalies, of a still more remarkable 

 character, is that in which there are no dissepiments, while 

 the placenta forms a distinct mass in the centre of the ovary, 

 as in Lychnis ; this is what is called a free central placenta 

 (fig. 134.). The first explanation of this peculiarity was to 



fig. 134. 



refer it to the theory of universal sutural placentation, upon 

 the supposition that in all such cases the dissepiments ori- 

 ginally meet in the centre ; but that subsequently the shell 

 of the ovary grows more rapidly than the dissepiments, and 

 breaks away from them ; while the excessive growth of the 

 placenta afterwards destroys almost all trace of the dissepi- 

 ments : their previous presence being only detected by lines 

 upon the shell of the ovary, or by the separation of the mass 

 of ovules into distinct parcels upon the placenta. 



Some years since it was thought that this was a perfectly 

 satisfactory explanation of the free central placenta, and I, 

 along with most other botanists, adopted that theory. But 

 it is undoubtedly a mistake. This has been skilfully and 



