STRUCTURE OF FRUIT. 155 



throughout its whole length, or only at the base ; but 

 its form and dimensions present some remarkable 

 differences, which modify the structure of the fruit. 

 Most frequently, it presents an elongated ridge bearing 

 one or two rows of seeds ; sometimes becoming very 

 large and thick, it extends into the interior of the cell, 

 forming a large projection, as is seen in Datura, 

 Solarium, Nicotiana, &c. ; sometimes it spreads out and 

 lines the whole of the retreating part of the carpel, as 

 is seen in the Poppy and Nymplicea; and at other 

 times, it is expanded into a kind of net-work, applied 

 to all the inner walls of the carpel, and bearing here 

 and there the seeds, as is seen in the Flacourtianeae and 

 Butomeae. 



The Cruciferae present, in this respect, an organization 

 which is peculiar to them ; the two carpels, which 

 compose the Siliqua (this is the name given to this 

 kind of fruit), have their retreating margins reduced to 

 an extremely thin and delicate membrane, which may 

 be regarded as an internal prolongation of the epicarp 

 alone, and the placentae are situated upon the margins 

 of the endocarp, which is not prolonged into the interior, 

 so that the seeds are parietal, although the fruit is 

 bilocular. 



All these various combinations are often rendered 

 obscure in fruits which open at maturity, by the different 

 modes of dehiscence ; and in indehiscent fruits by the 

 development of the pulp or flesh, which confounds their 

 different parts in an almost indistinct mass : these two 

 causes of obscurity, as well as those which proceed from 

 abortions or from the state of the central axis, deserve 

 to be analyzed. 



All the modes of dehiscence which we have found in 

 isolated carpels, may be met with in cohering ones, but 

 modified and multiplied by this cohesion. 



