THE FLOWER. 



29 



vertically, being at the same time broadened, and having the flowers more 

 or less thickly crowded together upon a common receptacle, which, in fact, 

 the depressed primary axis becomes. Here the outer bracts, commonly 

 numerous, constitute the involucre, and the inner ones that is, those 

 about the individual flowers are reduced to chaffy scales or bristles. 



FIG. 46. Stiiminate catkin of willow. 



FIG. 4?. Pistillate catkin of willow. 



In all these forms of inflorescence the lower or outer flowers expand 

 first, and the upper or inner last. There is, therefore, a movement from 

 the circumference toward the centre, and hence the inflorescence is 

 termed centripetal. 



FIG. 49. Vertical section of same. 



FIG. 48. A head (compound flower). 



Determinate inflorescence is much simpler and presents fewer 

 different forms. It comprises the cyme, fascicle, and glomerule. 



A cyme is commonly a flat-topped flower-cluster, like a corymb, only 

 it is produced in a different manner (Fig. 50). It presents several different 

 forms. 



