Abstract
Taking two varieties (A and B) nearly related but differed in the fertility of hyb.rids with the third variety(C), in the same way as mentioned in the preceding paper, ( I ), variation of good pollen percentage in (AxB) xC and Cx (AxB) was observed. Two kinds of variety combinations (l08x143) : 563 and (108x101): 521 were used (see Table I ). As demonstrated in the previous work, it was recognized again tb.at genes necessary for the development of gametes are duplicated and a hybrid befween varieties havir.g recessive genes at different loci produces double recessive or sterile ganietes in a deflnite ratio and thus resuIts hybrid sterility. In addition to this, CX(AXB) was found to segregate more sterile plants than (AxB)xC, and it was inferred that poiien possessing two dominant gamete-development-genes was lower in fertilizing capacity than pollen possessilng one dominant gene. This phenomenon seems to take some part, along with the degeneration of douhle recessive gametes, in the second and iater generations of a sterile hybrid to iricrease definit kinds of gene combinations which are simiiar with those of parental varieties.
