po t e I i a 



cestor, or are two distinct groups 

 in which the seed-habit has been sep- 

 arately evolved, must at present be 

 purely speculative. It is quite improb- 

 able that modern Pteridophytes rep- 

 resent, in any considerable degree, the 

 ancestral prototypes of the Angiosperms. 

 Nevertheless, interpretations of angio- 

 spermic structures must be cast in 

 terms of pteridophytic morphology. 



The characters assumed by the cot- 

 yledons of many Angiosperms upon 

 germination apparently place them in 

 the category of leaves, in fact the 

 resemblance is so marked that this 

 interpretation has been generally ac- 

 cepted by botanists without serious 

 question. Sachs writes : "We see that 

 Cesalpino uses the same word 'folium' 

 without distinction for calyx, corolla 

 and ordinary leaves ; just as he, and 

 Malpighi a hundred years later, un- 



