IPostelsta 83 



Summary. 



i. The typical embryos of the 

 Pteridophyta and Angiosperms differ- 

 entiate into three primary members — 

 the cotyledon, stem and root. 



2. Cotyledons are not arrested 

 leaves but are primarily haustorial or- 

 gans originating phylogenetically as the 

 nursing-foot in the Bryophytes and per- 

 sisting throughout the higher plants. 



3. The monocotyledonous condition 

 is the primitive one and prevails in 

 the Bryophytes, Pteridophytes, Mono- 

 cots and some Gymnosperms. The 

 two (sometimes more) cotyledons of 

 the Dicots are jointly the homologue 

 of the single cotyledon of the Monocots. 



4. The cotyledon always occurs at 

 the base of the primary stem. 



5. The hypocotyl is a structure pe- 

 culiar to the Angiosperms, being differen- 

 tiated between the primary stem and root. 



