BRITTLE RACES OF OENOTHERA LAMARCKIANA. 



701 



Table 111. 

 Crosses of oilier species with 0. scindens. 



in 1921; their seeds contained 8 per cent and 2 per cent of sterile 

 grains respectively. 



In all these experiments the culture of the hybrids embraced 

 59—60 seedlings. Those of 0. biennis Chicago x scindens had the 

 types of densa and laxa. Comparative cultures of the corresponding 

 hybrids of 0. Lamarckiana were used for the identification. I self- 

 fertilized some specimens in the cultures of 1920, and found only a 

 small amount of barren grains for both types in each of them. From 

 these figures it follows that 0. scindens has about an equal amount of 

 gametes of the types of laeta and velutina among its pollen, but the 

 reciprocal crosses show a deviation from the expectation correspon- 

 ding to the preferential fertilization in the velutina gametes (8). 



We may now consider the crosses with 0. Lamarckiana and 

 some of its mutants. In the first place, I have chosen 0. blandina, 

 which is a homogeneous race, and three other mutants, in which 

 the active pollen is also homogeneous. I shall first give the numerical 

 results, and afterwards compare them with the expectation as derived 

 from our formula. 



Table IV. 

 Homogeneous crosses of Oenothera scindens. 



