212 Humbert. 
We see that all of the constants, mode, mean, standard deviation, 
and coefficient of variability, for each of the six progenies of each 
of the three mother plants, vary greatly one from another. In the 
cases studied the buds seem to have varied almost as much on one 
plant as they do between different plants. 
While this data is not sufficient from which to draw iron-clad 
conclusions, yet there is enough to be very suggestive. To what 
extent may the plant be said to behave as an individual? is a 
question for further investigation. 
IV. Influence of food supply on Variation. 
The author wishes to include in Chapter IV that part of the 
data obtained from this study of Silene noctiflora which bears more 
or less directly upon the question of food supply as affecting variabi- 
lity. “More or less directly”, because in the “good soil” and “poor ~ 
soil” plots spoken of in this chapter there were other differences 
besides that of food supply. Table 3 under “Materials and Methods” 
gives the chemical analysis of the two fields, Plant Breeding Garden 
and Mitchell Farm, upon which the Silene experiment plots were 
located. Referring back to that table we see that as regards potassium 
and phosphorus they are about equal, the garden plot having a little 
more potassium and a little less phosphorus than the Mitchell Farm 
plot. Comparing the two as to organic matter content we see that 
the garden plot is much the richer as shown by the figures 9.35 % 
and 5.56 %. Along with this difference in the amount of organic 
matter we naturally find a much higher percentage of nitrogen in 
the garden soil. The figures are .25 % and .13 % N. Likewise high 
content of organic matter means large water holding capacity. It 
is readily seen that from the standpoint of chemical analysis we 
are justified in considering one soil much better adapted to plant 
growth that the other. The difference in favor of the Garden plot 
over the Mitchell Farm plot is also brought out by a casual exami- 
nation of the two soils and the size and thrift of the plants growing 
thereon. 
Comparing then pure line 250—11a, which was grown on the 
garden plot, with pure lines 220—11 U, 250—11 V, 250—11W, 250—11X, 
250—11Y, and 250—11Z, which were grown on the Mitchell Farm 
plot, we get a measure of the influence which this difference of food 
supply had upon the variability of the lines. The two constants, 
