1918} DEVRIES—MASS MUTATIONS 383 
often seen to decay, beginning in the lower part of the stem. Many 
specimens are lost from this cause during the summer. 
As given in table I, I cultivated the ochracea through three suc- 
ceeding generations, starting from the mutants of 1914. Two of 
them were self-fertilized; one yielded a progeny of 50 specimens, 
which constituted a uniform lot from the first beginning until the 
end of September. Among these I chose one of the strongest for 
self-fertilization, and had in 1916 from it a third generation of 58 
plants, all resembling their parent. Most of them have flowered. 
The other specimens of 1914 yielded seeds, some of which were 
sown in 1915 and some in 1916. In the first year I had 280 speci- 
mens, half of which flowered in August and September and were 
then pulled up, while the remainder flowered for the most part in 
October. They constituted a uniform lot of widely branched, low 
plants of pale green color. The culture of 1916 yielded 50 speci- 
mens, as pure and uniform as the former. 
I crossed the mut. ochracea with the parent species in order to 
study its hereditary character. I made the crosses in 1915 and got 
the following progeny in 1916: 
‘ grandiflora ochracea lorea Sum 
O. ochracea X grandiflora... ... 41 I I 60 
O. grandiflora Xochracea....... 35 16 9° sf 
ROR er 76 34 z nae 
POrCeNtAge. 66s es 68 31 I 
The two reciprocal crosses gave evidently the same result, show- 
ing that both parents are isogamic in respect to their differential 
character. For this reason I repeated the sowing in 1917, trans- 
planting the young seedlings after counting them, and determined 
the percentage of dying individuals besides that of the living 
ochracea. I found for two crosses of O. ochraceaX grandiflora on 
May 12, 23 per cent dead seedlings and 35-27 per cent living 
ochracea in a total of 226; means 17 and 31 per cent, together 48 
per cent. From the reciprocal cross I had only a small culture of 
55 seedlings, among which, however, none died in early youth, 
while the percentage of the living ochracea was.40. The figure for- 
ochracea is smaller than the highest one after self-fertilization 
