1918} DEVRIES—MASS MUTATIONS 405 
O. Lamarckiana X grandiflora lorea.—Culture of 61 plants, of 
which only one-half had been planted out on the bed and flowered 
in August. The other half consisted in July of 22 ovata, 4 lutea, and 
5 brunnea, giving almost exactly the same proportions as those on 
the bed. 
O. grandiflora XO. Lamarckiana nanella.—For this and the next 
crosses the dwarfs of the same race were used, as for almost all my 
previous crosses with dwarfs. I made the cross on two specimens 
of grandiflora in 1913 and sowed the seeds of one of them in 1914 and 
of the other in 1915. The first culture showed no contraria; the 
second, however, was extraordinarily rich in them. It contained, 
moreover, the /uéea specimen with the flowers of a gigas. 
The group of 1914 was the first of all my cultures to show the 
splitting. Before June only two types were distinguished, the 
yellow plants being considered as weak specimens of the main type. 
About the middle of June, however, they proved to have broader 
leaves and quite different flower buds, and were considered to con- - 
stitute a new type. The final proof of this conception was only 
reached in 1915, when I cultivated the second generation of the 
three types, and could observe their distinguishing marks on large 
sets of plants. In 1914 I counted one-half in the box, and the other 
at different times on the bed; the sum of the two groups is given 
in the table. 
The culture of 1915 confirmed that of 1914, apart from its 
mutants. I counted 11 ovata, 2 /utea, and 6 brunnea on the bed, 
besides 17, 5, and 8 of the same types in the box. These latter have 
not flowered, however, and for this reason are omitted in the table. 
O. grandiflora loreaXO. Lamarckiana nanella.—I -crossed a 
mutant Jorea in 1914 and a specimen of the second generation in 
1915. The first cross gave, besides the flowering individuals of the 
table, 39 ovata, 6 lutea, and 14 brunnea, which had not been planted 
out for lack of space, but confirm the results of the other set. 
Almost all of the plants of 1915 flowered in August. All these cul- 
tures have been conducted after the same principles, and this makes 
the description of further details quite superfluous. 
The current view concerning the mutations of Oenothera is that 
they take place during synapsis and that the sexual cells are in the 
