214 MASS MUTATIONS AND TWIN HYBRIDS OF 



of the first flowers. They gave the percentages shown in table III. 

 0. grandiflora x 0. Cockerelli. — Apart from the fact that all the 

 hybrids are of a normal green color, this cross simply repeats the 

 reciprocal one. I crossed two specimens in 1914 and had the first 

 generation of 80 individuals in 1915. They showed in July 52 per 

 cent laeta and 48 per cent velutina, with the same differences as 

 previously given and the same resemblance to the twins of 0. syrticola 

 x grandiflora. About one-half of the plants flowered, the flower 

 buds of the laeta being relatively thin, but those of the velutina 

 thick (5 x 20 mm.) and hairy. The second generation gave a uni- 

 form lot of 70 flowering plants for the velutina and a dimorphic 

 culture for the laeta. In this the types were exactly the same as in 

 the previous year. There were 57 laeta and 12 velutina, as counted 

 in July, when the differences were most sharp. 



O. grandiflora lorea x 0. Cockerelli. — Apart from the appearance 

 of a few individuals of the lorea type, this cross gives the same result 

 as the analogous cross of the species itself, and the hybrids are just 

 the same, not showing the least influence of the almost linear leaves 

 of the mutant mother. I made the cross twice, in 1914 and 1915. 

 The first one gave 80 specimens with 60 per cent laeta and 40 per 

 cent velutina, but without lorea. The second gave 81 flowering 

 plants, among which 23 were laeta and 58 velutina. Two weak spe- 

 cimens had the leaves of 0. grandiflora lorea. If we wish to explain 

 their occurrence we must, perhaps, take into consideration that 

 in cultures of hybrids of 0. Cockerelli with other species weak spe- 

 cimens with linear leaves are seen from time to time. In the second 

 generation I expected to find some specimens of lorea, but only 

 one appeared among the laeta. The culture embraced 64 plants, 

 with 49 laeta and 14 velutina. I also derived a second generation 

 from the velutina of the first; it had the same number of specimens, 

 all of which flowered, but they were wholly uniform and like those 

 just described. 



0. grandiflora x 0. biennis Chicago (cross of 1913). — First genera- 

 tion in 1915 with 40 flowering specimens, among which 12 were 

 weaker than the others from the very beginning, and proved in 

 August, when they flowered, to belong to the type of velutina, 

 having narrower leaves. There were still some doubts concerning 

 this identification, but they disappeared when the second genera- 

 tions were cultivated in 1916. These embraced the offspring of two 

 specimens of laeta, each consisting of 70 flowering plants, and that 

 of two velutina, with 47 and 60 specimens. 



