postelsta 75 



departure of the cotyledon in the Angi- 

 osperms from the ancestral pteridophy- 

 tic type. The embryo of a typical 

 Pteridophyte is attached to a fixed liv- 

 ing organism, growing on or in the soil. 

 All the nourishment absorbed by the 

 cotyledon is passed on directly and is 

 used by the continuously growing 

 embryo. The seed-habit, on the other 

 hand, divides the ontogeny into two 

 distinct periods of growth with an in- 

 tervening dormant period. The intra - 

 seminal life is a prolonged embryonic 

 period during which the plant depends 

 entirely upon neighboring tissues for 

 nourishment. In its own tissues or 

 with it in the seed must be stored a 

 food -supply which will enable it to 

 establish itself in an independent con- 

 dition on the resumption of growth. 

 While an Angiosperm embryo is obtain- 

 ing its independent condition the cot- 



