1917] DeVRIES— OENOTHERA 17 



nanella; the seeds of the one were sown in 19 14 and of the other 



in 191 5. There were no dwarfs in this first generation, but only 



laeta and velutina, which were just like those of the crosses already 



described. I had 90 and 72 plants, with 74 and 67 per cent laeta. 



There were 25 and 10 flowering plants belonging equally to the two 



groups; the others were large rosettes in June. 



If we compare the percentages of laeta given with one another we 



find for O. blandinaXO. Lamarckiana 41 and 54 per cent, for the 



reciprocal cross 22 and 25 per cent, and for the experiment with 



the dwarfs 74 and 67 per cent; finally, for the second generation of 



the first cross 33 per cent. The average of all these figures is 45 



per cent laeta , which comes as near to equality of the two groups 



as may be expected. The deviations from this mean are probably 



due mainly to the choice of the parents and to their cultural condi- 

 tions. 



O. rubrinervis XO. blandina. — besides the 3 crosses already 

 mentioned and discussed, I have also made the two reciprocal 

 crosses with my race of 0. rubrinervis. In the first generation they 

 split in the same way, the only difference being that instead of 

 the laeta another type arises. This is the subrobusta, which appears 

 in the hybrid splittings of O. rubrinervis with other derivatives of 



1 



O. Lamarckiana, as described in my Gruppenweise Artbildung. 

 No differences were observed, although the comparison lasted from 

 germination till the ripening of the fruits. The other type was the 

 same as in the crosses already dealt with, and exactly like the 

 parental type of O. blandina. 



The cross was made in 19 13 between an individual of my pure 

 race of O. rubrinervis and a specimen of the third generation of 

 0. blandina. One part of the seeds was sown in 1914 and another 

 in 191 5. In the first year I had 60 plants with 32 per cent blandina, 

 and cultivated 18 laeta and 7 blandina until the ripening of their 

 fruits. In the last named year I had 77 specimens, of which 61 

 per cent were blandina and of which 5 laeta and 5 velutina were left 

 to flower. All in all, the cultures embraced 137 plants, with 45 

 per cent blandina. The others were all subrobusta and not different 

 from the subrobusta cultures of those years resulting from other 

 crosses. 



