1918] . DEVRIES—MASS MUTATIONS 309 
into two types, 57 per cent being stout plants like biennis and 
reaching 1.5 m. in height when they flowered. The others lacked 
the initial rosettes but were not ochracea, evidently being lorea with 
the narrow, dark green leaves of this type. They were far less 
stout and reached only 1.20 m. in height and flowered some weeks 
later than the biennis. The mut. lorea grows always without a 
preparatory rosette and resembles in this respect the O. grandiflora. 
From this we may conclude that the splitting in our pedigree was 
exactly the same as that between the two species, with the excep- 
tion that the Jorea marks hid those of ochracea in the second genera- 
tion. 
I will now resume the results of the three crosses made with the 
pollen of O. biennis L. 
TABLE IV 
Crosses OF QO. grandiflora AND O. biennis, MADE IN 1914 
SECOND GENERATION FROM 
First GENERATION OCHRACEA 
SECOND 
Cross GENERATION 
Percentage Percentage | FROM BIENNIS 
Percentage | Percentage ¢ 
ochracea biennis ssa ee and} “ biennis 
O. grandiflora x biennis| 17 83 67 ochracea 33 uniform 
O. grandiflora loreaX 
Dieknis. ak: i¢ 85 43 lorea 57 
O. grandiflora ochracea 
mA biennis. << o; UHOIM: ove cs 89 ochracea II RS in Sore 
If we assume that in O. grandiflora the mass mutation into 
ochracea takes place at the time of synapsis, and that the egg cells 
are therefore mutated before fecundation, we may deduce from 
table IV that normal egg cells of the species, after fecundation by 
O. biennis L., give uniform hybrids of the biennis type, whereas the 
mutated egg cells reproduce the type of ochracea. This would 
explain the dimorphous condition, where uniformity would other- 
wise be expected. 
O. grandiflora XO. suaveolens.—I made this cross on two speci- 
mens in 1915, but got a very small harvest of seeds, yielding only 
8 and 13 seedlings. In June the same two types were seen as in 
the cross of O. grandiflora Xbiennis. I counted 2 and 4 ochracea 
