REPRODUCTION BY SEED 181 
The head (Fig. 80) is the characteristic inflorescence of 
the Dandelion family, the scabious, thrift, etc. The 
flowers are small, very closely packed, and surrounded 
by a ring of small leaves (bracts). 
Fie. 79.—D1aGRAM OF CYMER. 
The umbel (Fig. 81) occurs in the Parsley family (the 
Umbelliferz), the onion, narcissus, pelargonium, etc. The 
flowers are again usually closely packed, and in some of 
the Umbelliferee-—e.g., hogweed—the outermost petals of 
Fie. 80.—Dr1acram or Heap (CaPiTuLum). 
each flower are enlarged to increase the size and con- 
spicuousness of the whole cluster. 
In considering the biological significance of the various 
forms of inflorescences, we see that in all cases the flowers 
are so arranged as to increase the chances of pollination. 
