SUMMARY. 253 



acter of the leaf-arrangement above and below. The 

 terminal leaf, of which normal instances are cited, is 

 held to be a primitive feature, as the phyton-theory 

 indicates ; from the facts of seedling-organization in 

 the two great classes, it is argued that that of Mono- 

 cotyledons is the most primitive. 



Finally, Adventitious Leaves are treated of ; these 

 mostly arise as a result either of mutilation or other 

 abnormal modes of stimulation. 



