i 9 22] STOUT— STERILITY 123 



plants, the flowers that opened normally during the time of self- 

 incompatibility were functional in compatible crosses. The re- 

 sults of a test of this sort are shown in fig. 5. The cyclic develop- 

 ment of self-compatibility with its coordination among the various 

 branches of an individual according to time of bloom is shown in 

 figs. 2 and 3. 



There is evidence from other species (Sirks 10) that various 

 grades of cross-compatibility may exist between the individuals of 

 the same race or species, that the group relations may be variable 

 in different cultures of the same species or race (East and Park 4), 

 and that in general cross-incompatibilities appear with much 

 the same irregularity in heredity and in expression as do self- 

 incompatibilities. 



The writer's studies with these plants have been chiefly con- 

 cerned with self-compatibility. In the species of Brassica studied 

 the cross-relations have not been studied sufficiently to state with 

 certainty whether the grades of cross-incompatibility undergo 

 cyclic changes like those of self-incompatibility, but perhaps it 

 may be assumed that certain of the weaker grades of cross- 

 incompatibility do thus operate. 



Heredity of mid-bloom self-compatibility in pedigreed 

 lines of descent 



In the first or "parent" series grown of both Brassica pekinensis 

 and B. chinensis, of a total of 253 plants there were 21 plants that 

 produced viable seeds to self-pollination during the period of 

 mid-bloom. From such seeds pedigreed progenies were grown 

 through two generations, to test the inheritance of self-compatibility 

 and to determine the result of repeated selection for this character. 

 A summary of the records for the various series and families grown 

 to date is presented in table I. In these records the first series of 

 plants grown are given arbitrary numbers. The number of a series 

 with that of the self-compatible plant used as a seed parent is 

 employed in designating the series of succeeding generations. 

 Thus the line of descent and the relationship of the various series 

 of sister plants are fully indicated. 



In one series of the selfed F x generation of B. pekinensis (series 

 1-2) comprising 88 plants, 24 were strongly self-compatible. In 



