62 EMBRYOGENESIS IN PLANTS 



brown and red algae, there is little in the initial development that is 

 strictly comparable with the embryogeny of land plants. But in all the 

 larger, more advanced and elaborate forms, especially among the brown 

 and red algae, the details of the early development are closely 

 comparable with what we find in archegoniate plants. The early 

 determination of polarity, the axial development, the early inception 

 of a self-determining, distal growing point, the regularity of the seg- 

 mentation pattern, in short, all the developments by which embryos 

 are usually characterised and described, are found in the algae. These 

 parallelisms are the more remarkable in that in the algae the develop- 

 ment takes place in a purely aquatic environment and independently of 

 parental nutrition. 



