52 



STRUCTURAL AND PHYSIOLOGICAL BOTANY. 



426. These partitions are called dissepiments. 



427. Each dissepiment is therefore formed of two layers. 

 But these often grow together so intimately as to form but one 

 layer. 



428. Such being the origin of the -dissepiments, it follows 

 that, 



429. All dissepiments are vertical, and never horizontal. 



430. They are uniformly equal in number to the carpels out 

 of which the pistil is formed. 



431. A single carpel can have no dissepiment whatever. 



432. It will also be apparent, that as the stigma must bear 

 the same relation to the dissepiments as the point of the leaf 

 to the sides of the lamina, the stigma will always be alternate 

 with (between) the dissepiments. 



433. When the dissepiments of a many-celled pistil are 

 contracted so as not to separate the cavity into a number of 

 distinct cells, but merely project into a cavity, the placentae, 

 which occupy the edges of these dissepiments, become what is 

 called parietal ; Ex. Poppy ? r . Occasionally the placentae are 

 diffused over the whole face of the dissepiments, as in Bu- 

 tomus. 



434. A one-celled ovary may also be formed out of several 

 carpels, in consequence of the obliteration of dissepiments ; 

 Ex. Nut. 



