OENOTHERA GRANDIFLORA AIT. 213 



parents, 0. suaveolens lutescens and 0. grandiflora ochracea. They 

 must evidently be ascribed to the same mutability. Their flowers 

 were intermediate between those of the parents. It should be noticed 

 that this is the only case among all the experiments given in table 

 III in which a third type showed itself besides the ordinary twins, 

 apart from stray mutants 1 ). This shows that a special feature of 

 mutability in 0. suaveolens must be responsible for it. 



0. Cocker elli x 0. grandiflora. — Since 0. Cocker elli is an iso- 

 gamic species, the results of both the reciprocal crosses are the 

 same, with the exception that the hybrids of the cross just named 

 are liable to be more or less pale in their foliage, as is so often the 

 case in crosses in which 0. Cockerelli is the female parent, as for 

 example in 0. Cockerelli x suaveolens. In our case it is the laeta 

 which show this insufficient development of the chlorophyll, whereas 

 the velutina is dark green. The main interest of these crosses lies in 

 the fact that their laeta do not give a uniform progeny, but split 

 into laeta and velutina, exactly as in the case of the hybrids of 0. 

 Hookeri and 0. Lamarckiana (5). The velutina constitute constant 

 races in both instances. 



I made the cross 0. Cockerelli x 0. grandiflora twice, once in 

 1914 and once in 1915. They yielded 58 and 64 offspring, among 

 which 33 and 28 per cent were laeta and 67 and 72 per cent velutina. 

 These twins resembled those of 0. Cockerelli x 0. Lamarckiana, but 

 some of the laeta had a yellowish green foliage and were more or 

 less weak in constitution for that reason. The laeta had broad leaves 

 (4.5 x 15 cm.), whereas those of the velutina were narrow (3 x 15 

 cm.), and the same difference prevailed between the bracts of the 

 spike. This character was very conspicuous on the beds, especially 

 when compared with the cultures of the next generation. Moreover, 

 I had a lot of 0. syrticola x 0. grandiflora at the same time and 

 found the types of both twins to be essentially the same as in this 

 cross. 



In the second generation the velutina were uniform and repeated 

 the characters of the parent. The culture embraced 70 flowering 

 plants. They were a strikingly uniform lot, and made the distinc- 

 tion of the two types in the first generation as well as among the 

 progeny of the laeta easy. These latter consisted also of 70 flowering 

 specimens, which were counted in July, shortly before the opening 



*) Mutants of the ochracea type were seen among the laeta of the second gene- 

 ration from O. grandiflora X Chicago; see later. 



