IN DETAIL 



297 



are consequently much less conspicuous than the facies. A close inspection 

 of the societies formed by principal species shows that they are far from 

 uniform. Since they usually fail to exhibit distinct parts, it becomes neces- 

 sary to approach the question of their structure from a new standpoint. 

 Such is afforded by aggregation, which yields the simplest group in vegeta- 

 tion, i. e., that of parent and offspring. This is so exactly a family in the 

 ordinary sense that there seems to be ample warrant for violating a canon of 

 terminology by using the word for this group, in spite of its very different 

 application in taxonomy. It has already been shown that aggregation fur- 

 ther produces a grouping of families, which may properly be called a corn- 



Fig. 78. Calthettim (Caltha Icptoscpala) , a consocies of the alpine bog 

 formation. 



raunity. As they are used here, family and community become equally ap- 

 plicable to the association of plants, animals, or man. Both families and 

 communities occur regularly in each society of the formation, and they repre- 

 sent its two structures. In some cases, all the families are grouped in com- 

 munities, two or more of which then form the society. Very frequently, 

 however, families occur singly, without reference to a community, and the 

 two then constitute independent parts of the same area. This is typically 

 the case wherever gregarious species are present, since these are merely 

 family groups produced by aggregation. 



