A. B. Stour 93 
assign the decided variation in the grouping of cross-incompatibilities 
to variations in linkage relations. 
The available data on cross-incompatibilities in different species 
indicate marked variation in the group relations. East and Park report 
that the members of a seed progeny fall into classes which exhibit 
intra-class sterility but complete inter-class fertility. Thus if any two 
plants of a progeny are cross-sterile they will behave the same to a 
third plant. This rule does not agree with the relations reported by 
Correns (1912) for Cardamine pratensis, nor with the still different 
relations which Sirks reports for Verbascum phoeniceum. 
East and Park give conclusive evidence that there is wide variation 
in the number of groups, and the number of individuals in the various 
groups within a seed progeny. For example, in one progeny of 53 plants 
there were three well defined groups of 22, 16 and 12 individuals; in 
another there were five groups of 8, 3, 4, 3 and 2 plants; ae 
progeny of only 18 plants fell into six classes (4, 5, 3, 2, 2 and 2); another 
was composed of six classes of 4, 5,7, 5,3 and 3 plants; another showed 
marked inequality of four classes with 34,11, 4 and 2 individuals per 
class. East and Park assume that these irregularities are due to 
variability in linkage relations. Their further assumption that the 
pollen grains of a plant all operate alike does not hold for many feebly 
compatible self- and cross-fertilizations that are operating periodically 
or indiscriminately. The variations in cross- and group-relations are 
quite in harmony with the wide variations that appear in the sex 
relations of the organs produced by individual plants. 
PRESENTATION OF NEW Data. 
I. Relation of vegetative vigour and maturity to variations in 
self-fertility and self-sterility. 
End-season fertility is one of the clearest evidences of the fluctuating 
nature of the relations of the sex organs in plants that are feebly self- 
incompatible. It indicates, as does also mid-season self-fertility, the 
cyclic nature of life processes, and supports the doctrine that sexuality 
is itself fundamentally a function of maturity. 
In the experiments here reported controlled self-pollinations at 
frequent dates throughout the entire period of bloom were made. The 
evidence is clear that end-season fertility is comparatively rare, and 
is not a condition commonly operating in and characteristic of self- 
