192 VEGETABLE ORGANOGRAPHY. 



which the same naturalist names Omphalode, and 

 which occupies almost all the rest of the hilum, is 

 slightly convex in the centre, and appears to be the 

 trace of the cicatrice of the nourishing cord. 



When the embryo is directed towards the hilum, the 

 vessels go directly from it to the chalaza, which is then 

 confounded with the hilum ; but when the embryo is 

 directed in the contrary way, the chalaza is very dis- 

 tinct from the hilum, and the umbilical cord is prolonged 

 through the mesosperm from the hilum to the chalaza; 

 this course of the fibres is called the Raphe, and appears 

 externally as a kind of little nerve. The umbilical cord 

 is a prolongation of the carpellary fibre, which bears the 

 seed, and is itself prolonged into the raphe ; the cha- 

 laza is the true hilum, that is to say, the point where 

 the embryo draws its nourishment from the mother 

 plant; but it is often difficult to determine its position, 

 both on account of its small size, and of the change of 

 position of the embryo during the growth of the seed. 



There are some Monocotyledonous seeds, in which the 

 radicle causes by its position a little projection on a given 

 part of the spermoderm ; and at the period of germina- 

 tion it shoots out from this part ; it is doubtful whether 

 it be an organ properly so called, seeing the small num- 

 ber of plants in which it is found. 



Section III. 



Of the Albumen. 



If we examine an ovule at the period of flowering, 

 we find its spermoderm already well-formed, and its 

 canty filled with a mucilaginous fluid, to which the 



