Ti THE AMERICAN NATURALIST. [VOL XXXVI. 
is between the observed variation and the environment, or 
between parts of the same plant. Secondarily, it was hoped 
that this research might show something of the applicability 
of these methods to taxonomic or monographic work in a genus 
so difficult from the systematic standpoint as Aster. 
II. MATERIAL. 
This consisted of the blooming capitula of Aster shortzi 
Hook., A. nove-anglie 1., A. puniceus L., and A. prenanthoides 
Muhl. 
The capitula were cut off without any conscious selection, 
folded in papers, labeled, and preserved in alcohol. With the 
exception of those plants where series of pickings were made, 
the stems from which the capitula had been gathered were 
preserved for future reference. 
All of the species of Aster studied are perennial, but they 
differ in the manner in which the annual stems are produced. In 
the following description of the material used in this study I 
shall use the term “ individual" in its broader sense, including 
all stems which have been derived from a single seed. 
Aster shortii Hook. has from one to three or four slender 
annual stems arising from a small perennial root. The material 
which forms the basis for the study of this species was obtained 
Sept. 26, 1900, and consisted of 226 capitula from three isolated 
individuals and from a group of ten stems growing near to each 
other. The stems of this group were probably mostly distinct 
individuals, though they may have been of close genetic rela- 
tionship. These plants grew in the thin limestone soil at the 
foot of the Niagara limestone cliffs bordering the northern end 
of Sheldon's Glen, one-half mile southeast of Yellow Springs, 
Ohio. 
Aster nove-anglie L. has a heavy mass of perennial roots, 
and from the base of the annual stems of one year's growth 
may arise a considerable number of heavy stems of the next 
year's growth, forming a clump. The 199 capitula used in the 
study of this species were collected Sept. 30, 1900, from five 
individuals growing in the flood plain of a tributary to the Glen 
