1 22 Self Incompatibility in Hermaphrodite Plants 



was determined by controlled self-pollinations involving over 80,000 

 flower heads and about 600,000 individual flowers, show conclusively 

 that self-compatible plants occur sporadically among the progeny of self- 

 incompatible plants, and that self-incompatible plants continue to appear 

 among the offspring of self- compatible plants. Either self-compatibility 

 or self-incompatibility can arise from the other in a line of inbred or 

 selfed progeny ; in this sense the two conditions are reversible. Since 

 this is the case, dominance or recessiveness of these characters cannot be 

 adequately determined. 



None the less there is a tendency to heritability in these characters. 

 Self- fertile plants appear to constitute from to 10 °/„ of the progeny of 

 self- sterile parents. The proportion of such plants immediately increases 

 in the /jj in this generation of the red-leaved Treviso numbering 

 351 plants (Table IV), 30% of the plants were self-fertile to some 

 degree. In other families the percentage was higher (Table VIII, 1918). 

 The offspring of self-fertile plants are more likely to be self-fertile by a 

 proportion of about 5 to 1. This proportion can be changed only slightly 

 by the selection of parents of different degrees of self-fertility. 



Certain lines and families appear to maintain somewhat different 

 grades of self-fertility. This is most marked in respect to the range of 

 individual self-fertility. All families agree in general behaviour as to 

 regression, but some are more highly self-fertile than others. The 

 character of self-compatibility is one of incomplete heredity; a self- 

 fertilized line of descent does not breed true ; in pedigreed lines of 

 descent the characters self-fertility and self-sterility are reversible. 



From the standpoint of a factorial description of the results obtained 

 in chicory, several points are of significance. The spontaneous occur- 

 , rence of self-compatible plants after several generations of self-sterile 

 parentage suggests the phenomenon of mutation referable to single 

 factors or to the recombination of modifying multiples. But submitted 

 to the test of self-breeding the character of self-fertility does not breed 

 true, hence any particular factors or combinations that may be assumed 

 are not stable. The frequency distribution for fertilities suggests 

 variation that is often interpreted in terms of multiple factors of quanti- 

 tative and modifying values, and this is also suggested by the evidence 

 that certain families exhibit somewhat different degrees of self-compati- 

 bility. Yet in all families there is marked regression to self-sterility. 

 Perhaps the most significant fact from the standpoint of hereditary 

 analysis is that the proportion of self-fertile to self-sterile plants in the 

 progenies of self-fertile plants seems to fluctuate about a 1 : 1 ratio. This 



