DICOTYLEDONS: ARCHICHLAMYDE^E 



283 



dioecious ( 137) and wind-pollinated. A very character- 

 istic flower-cluster occurs in many of these forms, being a 

 spike-like cluster, but having conspicuous scales or bracts 

 subtending individual flowers or small groups of flowers. 

 It is called the 

 ament or catkin; 

 and familiar illus- 

 trations are found 

 on willows (Fig. 

 278), cotton woods, 

 birches, and alders 

 (Fig. 279). Both 

 staminate and pis- 

 tillate flowers, or 

 only one kind, may 

 be in aments. 



In higher fami- 

 lies with more con- 

 spicuous and usual- 

 ly insect-pollinated 



flowers, other common trees occur, as the tulip-tree (white 



poplar), magnolia, lin- 

 den, maple, buckeye, 

 box-elder, locust, sweet- 

 gum, and tupelo (black- 

 gum); and among the 

 Sympetalse the ash be- 

 longs. The very names 

 of these trees suggest 

 the characteristic forms 

 of our great deciduous 

 forest, which once ex- 

 tended in almost un- 



FIG. 278. 



.1 K 



Catkins of willow: A, staminate; , pis- 

 tillate. 



n 



n 



B 



Fio. 279. Catkins of alder; ^4, branch with 



staminate (n) and pistillate (m) catkins; broken SW66P from the 

 B, pistillate catkin in the next year (when 

 the seeds are ripe). After WARMING. 



prairies to the Atlantic 



