FERTILITY OF PARENT SPECIES AND HYBRIDS. 83 



Bateson and Piinnett (Bateson 1913) have reported a case of simple 

 Mendelian inheritance of sterility in sweet peas, in which normal 

 anthers were dominant to sterile anthers. The case is complicated by 

 coupling with a color factor. 



Biffen (1905) crossed species of barley having well-defined grades of 

 fertility. His results showed that the hooded barleys, Hordeum trifur- 

 catum and H. hexasticofurcatum, which are more fertile than the normal- 

 awned barleys, were dominant to four different species of the latter 

 kind. Segregation took place and it was inferred that only one allelo- 

 morphic pair of characters was involved. In other crosses between 

 well-defined tj^pes of barley he found various kinds of sterility dominant 

 over the normal perfectly developed floret. " In these cases the various 

 degrees of sterility, ranging from complete suppression of the repro- 

 ductive organs in the lateral florets to reduction in size only, are clearly 

 dominant over the perfectly developed floret." Here, again, the classes 

 obtained in the F2 generation gave evidence of a simple segregation. 



Brainerd (1907), in his resume of the interesting behavior of certain 

 hybrids between violet species, reports that pronounced degrees of 

 sterility occurred in some of the crosses. When the hybrids were 

 mated inter se he recovered plants of normal fertility in the F2 genera- 

 tion. In discussing the phenomenon of this segregation of normally 

 fertile strains from an almost sterile hybrid Fi generation, he says: 



'"With this diminution or entire loss of hybriditj^, we should expect a 

 partial or total recovery from the impairment of fertility produced in the first 

 cross. At any rate, it is an observed fact that many violet seedlings whose 

 hybrid parents produced seed from only about one-tenth of their ovules, are 

 themselves normally fertile." 



We are still at a loss to know whether the fertility returned because 

 there were recombinations of definite factors for fertility or because 

 the simple recovery of parental types gave fertility like the parents. 

 In the latter case the sterility of the Fi hybrids might be thought to 

 be due to disturbances arising from the admixture of widely diverse 

 germinal elements, and a subsequent segregation of the parental types 

 would mean a combination of factors and characters from one source, 

 and with these the fertility of this parental t>^e. But if fertility and 

 sterility are due to independent factors, one should be able to combine 

 the characters of either parent with fertility or sterility, or degrees of 

 either. 



DeVries (1909) found that Oenothera lata produced no fertile pollen, 

 although it was normally pistillate. The anthers showed all conditions, 

 from the absence of grains to normally developed pollen, but they were 

 always sterile. He was able to fertilize 0. lata with pollen from 0. 

 lamarckiana. The anther sterility was transmitted through the ovules 

 of 0. lata, but was coupled with other 0. lata characters, for it segre- 

 gated out associated with them. 



