42 COMMUNITY FUNCTIONS— DYNAMICS OF BIOTIC FORMATION 



the deposit of pollen, as illustrated later under pollination coactions. 

 In the community sense, the complete floral cycle includes not merely 

 the behavior of flower and cluster, but also the interaction of these 

 with the deportment of the pollinator. While the general subject of 

 pollination has received much attention since the time of Darwin 

 especially, complete and detailed life histories have been a matter of 

 recent concern (Clements and Long, 1923; Clements and Clements, 

 1913, 1928). 



Fig. 2. — Round-of-life in the flower of wild onion (Allium cernuum) ; Alpine 



Laboratory, Pikes Peak, Colorado. (Drawn by Edith Clements; courtesy of 



Carnegie Institution of Washington.) 



Fruiting and Seed Production. In the great majority of species, 

 the pistil merely enlarges with the developing ovules to constitute the 

 fruit, but in many others another part of the flower shares in its forma- 

 tion. Such changes are not only of interest as a late phase in the 

 life cycle of the flower, but they are likewise of much importance in 

 connection with coactions concerned with food and with dissemination. 



Dissemination. Plants fall into two general groups, in accordance 

 with the presence or absence of special devices that aid in the dis- 

 tribution of seed or fruit. Many species possess no such modifications, 

 and their dissemination is chiefly a matter of chance operating upon a 

 high seed production. On the other hand, a vast number exhibit some 



