490 



STRUCTURE AND LIFE HISTORIES 



be considered again later on (page 608). In treating of 

 the dicotyledons first, however, we have tacitly assumed 



YiG^ 374.— Cat-tails. Typha angustijolia at left; Typha latifolia at right. 

 Staminate flowers above; pistillate flowers below. 



that they are the older forms, from which the mono- 

 cotyledons have been derived. 



