32 KAPHE ARIL. [BOOK i. 



The raphe is always a true indication of the face of the 

 seed ; and it is very remarkable that the apparent exceptions 

 to this rule only serve to confirm it. Thus, in some species 

 of Euonymus in which the raphe appears to pass along the 

 back, an examination of other species shows that the ovules 

 of such species are in fact resupinate ; so that, with them, the 

 line of vascularity representing the raphe is turned away from 

 its true direction by peculiar circumstances. In reality, the 

 chalaza is the place where the secundine and the primine are 

 connected ; so that in orthotropal seeds, or such as have the 

 apex of the nucleus at the apex of the seed, and in which, 

 consequently, the union of the primine and secundine takes 

 place at the hilum, there can be no apparent chalaza, and 

 consequently no raphe : the two latter can only exist as 

 distinct parts in anatropal or amphitropal seeds, where the 

 base of the nucleus corresponds to the geometrical apex of 

 the seed. Hence, also, there can never be a chalaza without 

 a raphe, nor a raphe without a chalaza. 



It is usual to speak of the aril of plants (fiys. 189 and 

 190.) when speaking of the ovule; but it more properly 



comes under consideration along with the ripe seed. As a 

 general rule, it may be stated, that everything proceeding 

 from the placenta, and not forming part of the seed, is refer- 

 able to the aril. Even in plants like Hibbertia volubilis and 

 Euonymus europseus, in which it is of unusual dimensions, 



