236 G. Udny Yule . 
These passages give the aim of Professor Johannsen’s work, 
viz. the elucidation of the statistical laws of heredity for the race by 
the study of the corresponding laws for the “ pure line,” i.e. the 
posterity of a single self-fertilised individual. The results of three 
researches are given, the first two referring respectively to the 
weight and the length-breadth ratio of the seeds of Phaseolus 
vulgaris, the third to the phenomenon of relative sterility in barley 
as measured by the percentage of buds in a head failing to set seed. 
The barley used was a variety of three-rowed chevalier-barley. 
For details the reader must of course refer to the original, but the 
method of the chief experiments may be illustrated by reference 
to those on the weight of beans. A single bean of known weight 
was taken, sown, the resulting plant allowed to self-fertilize (in a net- 
covered enclosure) and its seeds harvested. These seeds or a 
sample of them were sown in their turn, allowed to self-fertilize 
under similar conditions, and their seeds harvested. The mother 
seeds and their offspring were then weighed, and the results collected 
in the following form. (All weights are stated in milligrams). 
LINE A. 
Weight of the ancestral bean ca. 800. 
Average weight of the mother-beans ca. 600. 
Weight of the 
mother-beans. 
Characters of the Offspring. 
Average weight. 
Number. 
Standard 
deviation. 
550—600 
605 
15 
126-8 
600—650 
642 
39 
107-9 
650—700 
635 
45 
105-8 
700—750 
661 
46 
112-4 
The whole line 
641-9 
145 
109-5 
Details are given for nineteen such “ pure lines ” as regards the 
weight of the beans and for twelve lines as regards the length- 
breadth ratio; the barley is treated in much less detail. The 
results are very simply summarised by dividing each set of “ mother- 
beans” into two classes, “minus-variants” and “plus-variants,” 
and expressing the mean weight of the offspring of each of these 
classes as a percentage of the mean of the line. The results for all 
the different lines can then be grouped together (Table 4, p. 37). 
