CH. X] EMBRYO. 139 



It is interesting to note that the embryological develop- 

 ment of the sporophyte begins by a cell-wall cutting the 

 egg-cell into two halves, one of which has the general 

 character of stem, the other of a root. It is one of the 

 many instances of the early differentiation of plant- 

 embryos into what are known as a shoot-half and a 

 root-half. 



