A. B. Stout 93 



assign the decided variatian 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 Gardamine pratensis, nor with the still different 

 relations which Sirks reports for Verhascmn phoemceum. 



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 ; another 

 progeny of only 18 plants fell into six classes (4, 5, 3, 2, 2 and 2); aruother 

 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, Melation 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- 



