84 GATES: THE VALIDITY OF HELIANTHUS ILLINOENSIS 
season to season and even within a given season. This has a 
decided effect in the production of the subspecific type, as is shown 
in the following examples. The spring and the first part of the 
summer of 1908 were characterized by extreme and protracted 
drought in Illinois. During that time, almost without exception, 
plants of this sunflower were densely pubescent and had long inter- 
nodes, whether they occurred in sun or in shade, in poor soil or in 
a richer soil. This is characteristic of 7. occidentalis illinoensis. 
The drought was broken in August in Lake County, Illinois, and 
the result was that virtually all the plants, some of which had 
been definitely marked, lost their pubescence and to all intents 
and purposes were normal ZH. occidentalis. The season of 1909 
had abundant precipitation throughout and during that entire year 
but very few plants were found that could be referred to 17. occt- 
dentalis illinoensis, even in patches which the spring before had 
been dominated by that type. 
Flelianthus occidentalis easily maintains itself on the sand but it 
may also occur on black-soil prairies without apparent modifica- 
tion. In addition, it may occur on sand prairies where, near 
Winthrop Harbor at least, it is barely able to hold its own. In 
such situations, however, the plants are of the pubescent, long- 
internode type. The subspecific type, termed /7/. occtdentalis 
ilinoensis, always occurs in sandy soil, within or near the limits of 
the Quercus velutina association, where it is a response to edaphic 
conditions in the environment which increase the amount of food 
supply or which increase the transpiration on a soil more or less 
deficient with respect to either or both of the factors, physiological 
water supply and food materials. 
The preceding conclusions have been based on field observa- 
tion alone. Culture of the plants under control conditions will in 
the future give more conclusive results. 
URBANA, ILLINOIs. 
