THE FLORA!. SffOOT. 



420 



falls away after the maturity of the flower or fruit, is called & 

 catkin, or an ament. The flower clusters of the alder, willow, 

 (fig. 555), poplar, and the staminate flower clusters of the oak, 

 hickory, hazel, birch, etc., are aments. So characteristic is this 



Fig. ^51. 



Head of sunflower showing centripetal inflorescence of tubular flowers. (Photo 

 by the Author.) 



mode of inflorescence that the plants are called amentijerous, or 

 amentaceous. 



828. Anthesis of flowers with indeterminate inflorescence. 

 In the anthesis of the raceme as well as in other corymbose forms 

 the lower (or outer) flowers being older, open first. The open- 

 ing of the flowers then takes place from below, upward; or from 

 the outside, inward toward the center of inflorescence. The 

 anthesis, i.e., the opening of the flowers of corymbose forms is 

 said to be centripetal, i.e., it progresses from outside, inward. 

 The anthesis of the fuller's teazel is peculiar, since it shows both 

 types. There are several distinct advantages to the plant where 



