STRUCTURE OF FRUIT. 159 



when each of them remains entire, and double this number 

 when there is a fissure of the middle nerve. The same 

 kind of dehiscence is produced in the Poppy by a 

 different cause — the existence of the torus in a mem- 

 branous state surrounding the carpels. 



5th. The contrary, also, sometimes takes place, as in 

 Cuscuta, for example, where the carpels are more 

 united at the apex than at the base, and separate at 

 maturity at the lower extremity; this constitutes 

 Basal dehiscence, which is almost always slightly 

 irregular, and is nearly confounded with transverse de- 

 hiscence. 



Gth. Lastly, it sometimes happens, even in dry poly- 

 spermous fruits, that the carpels are so united together 

 that they cannot separate or split regularly by any part 

 of their surface ; there generally result, then, towards 

 the top of each carpel, kinds of pores, or irregular 

 ruptures, which give passage to the seeds, but which can 

 only be placed among dehiscences called Irregular; 

 we see it in Linaria and several other Scrophularinese. 



In indehiscent fruits, the true nature of the carpels is 

 obscured by causes differing from the preceding ; some- 

 times the fruits do not open, because the pericarps are 

 membranous and dried up, and then there is usually an 

 abortion of several parts ; sometimes they are indehis- 

 cent because they are fleshy : and here we find the same 

 distinctions as among fruits with isolated carpels ; the 

 flesh, which is only a development of the mesocarp, is 

 found outside the cells, and the pulp is found inside 

 them : there are fruits, as the Quince, which have flesh 

 and pulp at the same time. Generally, in fleshy fruits, 

 we cannot easily recognise the original position and 

 place of the carpels, because the unions here are much 

 more intimate. 



A frequent cause of error in the manner of appreci- 



