362 



OENOTHERA RUBRINERVIS, A HALF MUTANT. 



one. On the other hand, I have repeated the cross with 0. Hookeri, 

 in the progeny of which I had previously not been able to distinguish 

 the twin types. I had in 1916 the cultures given above. Most of thees 

 plants flowered in August. 



The results coincide with the previous ones as nearly as might 

 be expected. The types of the twins were the same as those in the 

 older cultures. 



For these twins I have determined the amount of empty grains, 

 self-fertilizing two specimens of each of them in August 1916 and 

 counting out 100 seeds for each parent. 



Percentage of germs in seeds of laeta and velutina 



As in other cases, the seeds of the laeta hardly contain any empty 

 grains, whereas those of the velutina are often badly developed. 



My task was now to repeat these crosses, substituting 0. mut. 

 deserens and 0. mut. velutina for O. rubrinervis. The latter group 

 of crosses have already been described elsewhere 1 ), they yielded 

 pure cultures of velutina which in every case were exactly like the 

 velutina of the corresponding cross with 0. Lamar ckiana. The crosses 

 with 0. deserens were made in 1915 and their progeny studied in 

 1916; it was in every case wholly uniform. 



About one-half of each culture flowered and developed their fruits. 

 For each culture a control parcel was cultivated with the laeta from 



l ) Kreuzungen von Oenothera Lamarckiana mut. velutina. Zeitschr. f. Ind. Abst. 

 17 : 1917. Opera VI J, p. 317. 



