358 SEMI-CENTENNIAL OF TORREY BOTANICAL CLUB 
flowers produced per head. The nature of the partial variabilities 
was found to be such as to afford special opportunities for analyses 
of the intraseasonal and interannual variability and for a study of 
variation among heads according to position on a plant. The 
data were so collected that individual variabilities could also be 
determined. As the studies progressed interest extended to a 
study of heredity and the effects of selection in the different races 
which appeared and which were grown in pedigreed cultures. 
MATERIAL AND METHODS 
Cichorium Intybus is in many respects especially favorable for 
such study. The flowers are conspicuous and with the exception 
of an occasional tubular flower are all ligulate. The flowers of a 
head are readily distinguished and easily counted, as all the 
flowers of a head are fully expanded at the same time. А head 
opens but once and is usually expanded but a few hours during 
the forenoon, a behavior that somewhat limits the amount of data 
that can be collected in a day, but makes the collection of data from 
day to day more simple, as there is no danger of recounting the 
same heads. The flower number per head is not excessively high, 
which with the disposition of expanded flowers makes accurate 
counts a simple matter. А considerable number of flower heads 
open each day during a rather extended period of blooming. The 
numbers during the greater part of the season are sufficient to give 
at least ten heads per day for study. The abundant branching 
and the development of a large number of heads in various posi- 
tions and at various times admits of rather full development of 
numerous parts of an individual and gives opportunity for the 
intensive study of various aspects of partial variability. The 
plants are, furthermore, hardy and easy to cultivate, so that 
numerous plants can be grown under as nearly the same conditions 
às is possible. 
The cultures of Cichorium Intybus studied were, for the most 
part, the same plants whose behavior in respect to sterility (due 
to physiological incompatibility) has already been reported (Stout, 
716,717); they include mainly two somewhat distinct groups of 
plants, as follows: 
In one group аге Е;, Fo, Ез, and Е, generations derived by 
