168 Observation of the Origin of Varieties. 
flowered altogether. I picked off and recorded a head 
from each of these during the course of the summer. 
On every plant I selected the terminal inflorescence of 
the main stem as soon as it opened ; plants in which this 
failed were pulled up before they flowered. Only pri- 
mary inflorescences were, therefore, employed, and the 
curve obtained was an index of individual variability, 
that is to say each unit in it represented a whole plant. 
The figures obtained are represented in the following 
series. The upper row gives the number of ligulate 
florets (L. F.) per inflorescence; the lower, the number 
of individuals which possessed these numbers. 
VARIATION IN NUMBER OF RAYS IN C. SEGETUM,, 1892. 
L. F. 12 13 14 15 16 17 18 19 20 21 22 
Individuals 1 14 13 4 6 9 7 10 12 20 1 
The curve based on this series of figures is given in 
Fig. 30. One of its two apices corresponds to that of 
the wild species, the other to that of the curve for Chry- 
santhemum Leucanthemum and C. inodorum. 
My next task was to separate the components from 
this mixture and to do this in such a way as to place their 
existence in the mixture beyond doubt. On account of the 
inevitable interference of insects in pollination it seemed 
to me impossible to do this for both supposed races at 
the same time, so I determined to isolate the 13-rayed 
form first, and the 21 -rayed later on from a new mixed 
crop. I devoted the two years 1893 and 1894 to the 
former inquiry. 
With this object in view, I eradicated every indi- 
vidual of the mixed crop of 1892 which had more than 
13 rays, as soon as I had counted the rays on its terminal 
flowerhead. In this way only 15 plants were saved, of 
which one had 12 and the rest 13 ligulate florets; the rest 
