98 Fertility in Cichorium intybus 



2 7o of the flowers set seed when self-pollinated ; in alfalfa 27 % of the 

 flowers were fertilized with self-pollen, and when Shirley poppies were 

 self-pollinated 39% of the flowers set seed." The performance of in- 

 dividual plants is not indicated in these results, so it is impossible to 

 judge of the variability in fertility that occurs in the various individuals 

 involved. Evidently some individuals are self-sterile (except in Trade- 

 scantia ?) and some are self-fertile. 



At this point one may venture to recognize that most of our mis- 

 understanding (and assumed understanding as well) of the transmission 

 of characters and of the nature of variation of all sorts is, no doubt, due 

 to attempts to analyze all sorts of characters in terms of hereditaiy 

 units. There has been a tendency to ascribe all sorts of characters, 

 superficial, fundamental, all sorts of pattern etfects in pigment dis- 

 tribution, minutelj' qualitative or quantitative differences of highly 

 specialized organs, and general qualities of an organism as a whole to 

 factors which, it would seem, are mostly thought of as corpuscular units 

 serially arranged in the germ plasm. The inadequacies of the attempts 

 to analyze self-sterility on this basis are quite apparent both as to 

 methods and results. 



To speak of the occasional appearance of self-compatible individuals 

 in an ordinarily self-sterile race as sporadic, and to refer the processes 

 determining the possibility of fertilization to variable interactions 

 between tissues and cells as such, may to many seem less definite than 

 an interpretation on the basis of assumed hereditary units. But the 

 irregular behaviour of compatibility and incompatibility both in ontogeny 

 and heredity in chicory is clear. Neither compatibility nor incompati- 

 bility are fixed and unchanging characters in transmission and in 

 expression, and are not to be considered as directly represented in the 

 germ plasm by hereditary elements. 



In general it has been held that functional sex-vigor is congenital, 

 and that fertility in the sense of ability to produce large numbers of 

 offspring is hereditary. In many hermaphrodite plants, perhaps the 

 majority, self-fertility appears complete; within many species cross- 

 compatibility is perhaps complete ; the functional compatibility between 

 the sexes is so general in the plant and animal kingdoms that it has 

 been held to be congenital. 



The presence of sexual incompatibility, therefore, between individuals 

 of a single race or variety, or even single line of descent, as it is found 

 in chicory, strikes one at first as a decided anomaly, and it seems still 

 more an anomaly that the sex organs produced on the same plant, and 



