posteisfa 79 



organize the huge bag-like proembryo, 

 while in Ginkgo they enter into a 

 compact tissue from which the embry- 

 onal stem and root primordia are later 

 differentiated. 



The so-called cotyledons of the 

 Gymnosperms are, so far as definitely 

 known, true leaves arising as exogenous 

 outgrowths upon the growing point of 

 the stem. 



Gnetum and Welwitschia in their 

 embryogeny show the least departure 

 from the pteridophytic type. Free 

 nuclear division does not take place, 

 the oosperm giving rise directly to a 

 suspensor on the end of which an 

 embryo is produced. When germinat- 

 ing, as the root pushes out from the 

 seed, there is developed at the base 

 of the stem a lateral protuberance 

 which remains in the seed and absorbs 

 nourishment from the endosperm and 



