I2 6 BOTANICAL GAZETTE [February 



highly self-compatible. Two series were grown from parents that 

 were self -incompatible. In one of these all of the 19 progeny were 

 self -incompatible; in the other series of 34 plants 27 were fully 

 self-incompatible, 5 were feebly self-compatible, and 2 were self- 

 compatible of medium grade during the period of mid-bloom. 



Summary. — The results obtained in these various pedigreed 

 cultures show that self-compatibility is a character which is not 

 directly hereditary. Self-compatibility occurs sporadically in a few 

 members of these prevailing self-incompatible species. This 

 character does not breed true. Selection for self-compatibility 

 does not immediately lead to the establishment of self-compatible 

 races. Neither is self-compatibility nor self-incompatibility domi- 

 nant in crosses. There is some indication, however, that certain 

 races may be secured in which the mode of distribution in respect 

 to self-compatibility is higher than in others. 



Discussion and conclusion 



The strains of Brassica pekinensis and B. chinensis studied 

 were previously selected and bred for excessive leafy growth rather 

 than for fruit and seed production, yet they are reproduced exclu- 

 sively by seeds. The vegetative vigor is not in the least utilized 

 in the development of parts which may propagate the plants 

 vegetatively. In their habit of growth and bloom, the stage of 

 sexual reproduction in these plants quickly follows a period of 

 remarkably vigorous vegetative development, hence these species 

 are favorable material in which to study the correlative relations 

 of the asexual or the vegetative phase to the sexual or reproductive 

 (by seeds) phase in the complete life cycle. 



The two types of sterility, impotence (including flower abortion 

 and arrested development), and proliferation, or the destruction 

 of a pistil by vegetative growth, as they occur in B. pekinensis and 

 B. chinensis, are both phenomena associated with the formation 

 of floral organs. The other type of sterility, physiological incom- 

 patibility or relative sterility which is present, is concerned with 

 the physiological inter-relations of the sex organs in the various 

 processes of fertilization. 



These three types of sterility develop and operate in these two 

 species and in their hybrids in intimate correlation with the cyclic 



