Stout & Boas: STATISTICAL STUDIES IN CICHORIUM 845 
Further analysis of intraseasonal variation has been made by 
Shull. He ('o2) made successive collections of heads of Aster 
prenanthoides and counted the bracts and the ray- and disk-flowers 
per head. The heads were taken from plants growing wild on a 
"single small plot" and were evidently collected indiscriminately. 
On the first date of collection records were made from 117 heads, 
on the second from 143, on the third from 139, and on the last 
from 116. The average number for all the organs counted de- 
creased in number as the season advanced.’ Later ('o4) he gives 
data for twelve successive collections, made from September 12 
to October 9 in 1903; the curves show low values at first, then a 
sudden rise, which is followed by a gradual decrease and a sudden 
rise at the end of the season. The rise at the end of the season 
can hardly be considered to be significant, since it was determined 
from only four heads. Shull attributes seasonal variability here 
observed chiefly to individual variability rather than to partial 
variability. He suggests that the low flower number seen early 
in the season is due to weak or starved individuals which bloom 
first and which have a lower flower number than is normal for the 
species, but his data being indiscriminate do not determine the 
facts regarding this point. Further, his view raises the question 
of the adequacy of judging vigor by the number of flowers per 
head. The data later presented in this paper for chicory will show 
that partial variability may have been involved as the principal 
cause of the seasonal decrease observed by Shull. 
V. OBSERVATIONS AND EXPERIMENTS ON THE INFLUENCE OF 
ENV 
With the recognition that the number of parts in an inflores- 
cence is often subject to considerable variability, certain experi- 
mental studies were made regarding the influence of nutrition. 
Some of these have a very direct bearing on the factors involved 
in both individual and partial variability. 
Weisse (97) sowed seeds of two heads of Helianthus annuus: half 
of the seeds of each was sown in pots containing sand, and half 
was sown in ordinary garden soil. The ray-flowers in the terminal 
heads were counted. The 155 heads from plants grown in sand 
had an average ray-flower number of 21 and a standard deviation 
