528 THE AMERICAN NATURALIST [Vol. LIII 



nodes bear short and frequently undeveloped lateral 

 branches, which usually appear so late in the season that 

 none of their heads, or only a part of them, open their 

 flowers before frost. In many plants only the uppermost 

 nodes bear branches at all, and in such cases the inflores- 

 cence is flattened or depressed. Every plant normally 

 bears the primary terminal head and few or several sub- 

 terminal heads and simple cymes from the uppermost 

 axils. The number of heads is at a minimum in shady 

 situations. The middle nodes bear floriferous branches 

 only on large plants of favorable situations, where there 

 is sufficient light and the plants are not crowded for space. 



A single cyme consists of two or more heads on pedun- 

 cles 1-3 cm. long with subulate bracts. Each peduncle 

 is usually accurately curved and leaves the straight axis 

 at a prominent angle, so that the true terminal heads are 

 easily recognized. The usual number of heads in each 

 cyme is two to five and the maximum number observed is 

 nine. A cyme of two heads consists of a terminal head 

 and an inferior lateral head. A cyme of three heads con- 

 sists of the terminal and {a) two inferior lateral heads or 

 [h) an inferior two-headed cluster. A cyme of four 

 heads presents the usual terminal head and {a) three 

 inferior lateral ones on separate peduncles or {h) one 

 lateral head and one two-hcadod cluster. One of five 



lateral head and a ihi-cc-hCadiMl vyww of citlirr of the 

 types mentioned al)ove or ih) two two-headed clusters. 

 Cymes of greater numbers of heads have the same gen- 

 eral structure, of a single terminal head with various 

 combinations of single inferior heads, two-headed clus- 

 ters and three-headed clusters. 



Three types of vai-iatimi wciv looked for in examining 

 the species: (1) a xariation hrtwccn ihe heads of each 

 cyme, possibly correlated with their i)osition, whether 

 terminal or in fcrioi' ; ( i' ) a \ ariation between different 

 tlorifei-oiis bi-jiMclies of the same plant, possibly corre- 

 lated with the aiiioiiiit of a\ailable nourishment; and (3) 



