stout: pollinations in cichorium intybus 347 



same plant) pollinations grew much more rapidly and there is 

 some evidence especially by Ulrich ('02) that in rye such pollina- 

 tions may be slightly more fertile than autogamous pollinations. 

 Such results suggest that the assumed individual stuffs are differ- 

 ent in different parts of the plant, and Jost even considers that 

 when self-fertilization occurs in varying degrees the cause is to be 

 sought in variations in the qualitative nature of the pollen. Fur- 

 ther evidences of such variation are seen in the experiments with 

 two plants of Hemerocallis flava which Jost found to be self-fertile 

 to some degree. This result he does not consider as proof that 

 Focke ('93) was wrong in reporting this species as self-sterile, 

 but that different races and even different individuals may exhibit 

 marked differences in the degree of self-fertility. 



Jost's facts are in accord with those of Darwin both in respect to 

 the fluctuating behavior of self-sterility and to the poor develop- 

 ment of pollen tubes, which is the rule in such cases. Darwin 

 considers that highest fertility in general is due to differentiation 

 in the sexual elements and that both the growth of the pollen 

 tubes and the mutual action of germ cells are improved by in- 

 creasing these differences, at least up to a certain degree. Jost's 

 view is based on the same underlying conception of sex. He 

 makes Darwin's assumptions of "differentiation" concrete by 

 assuming that the differentiation is one of chemical substances, 

 his individual stuffs. Each plant has its own individual stuffs 

 and hence when both reproductive organs and elements are 

 derived from a single plant they have the same individual chemi- 

 cal substance, and hence lack the differentiation necessary for 

 proper functioning. 



For the explanation of cases of feeble self-fertility, and Jost 

 expresses doubt that any hermaphrodite plant is fully self-sterile, 

 Jost assumes that individual variations may exist among the 

 pollen grains, giving qualitative differences quite equal to that of 

 the individual stuffs in different plants. Jost presents some 

 evidence that geitonogamy is more effective than autogamy, 

 but does not develop the idea that the variation in self-fertility 

 may have any relation to the actual physical relationship of the 

 organs concerned with respect to relative location on a plant. 



With reference to the production of differentiating chemical 

 substances both of specific and individual sorts, Jost states: "Man 



