612 



WEED FLORA OF IOWA 



Fig. 471 I 



Fig. 471 II 



Fig. 471 III Fig. 471 IV 



Fig. 471. Types of inflorescence. I. Raceme of Currant. II. Umbel-like 

 inflorescence of Cherry. III. Head of Clover. IV. Umbel of Parsley. 



If the lowest pedicels or flower stalks are elongated (or the upper 

 ones remain short) so that the cluster is convex or nearly flat on 

 top, we have the corymb type of inflorescence. 



In the wild carrot, common yarrow, and parsley family in gen- 

 eral, the axis of the corymb is so much shortened that all pedicels 

 seem to start from the same point and resemble the rays of an in- 

 verted umbrella. This is the umbel. 



In the clover {Trifolium procumtens) the flower axis is short 

 and the pedicels of the flowers are either short or absent. This 

 causes the flowers to be crowded into a roundish cluster which is 

 called a head. 



