1915] DE VRIES—OENOTHERA BIENNIS 181 
From these discoveries it was pretty safe to deduce that the 
pure O. biennis must also be in a state of mutability, and the first 
thing to do was obviously to make extensive cultures in order to 
find the pure line mutants. Srtomps cultivated over goo individuals 
of the third and fourth generations of a pure line, derived from a 
rosette collected by him in the sand dunes near Beverwyk, Holland, 
in 1905. Among these he found one O. biennis mut. nanella, one 
O. biennis mut. semigigas, and also four instances of the pale- 
yellow variety O. biennis sulfurea. The first two he calls parallel 
mutations, since they are analogous to the dwarfs and semigigas 
mutations of O. Lamarckiana and arise in the same way and with 
the same differentiating characters. The experimental origin of 
O. biennis sulfurea by mutation clearly shows that this variety, 
which is anything but rare in some parts of our sand dunes, may 
arise in the same way in the wild condition and afterward propa- 
gate itself by seeds. 
The production of dwarfs from O. biennis by mutation has 
since been repeated more than once in my cultures of hybrids 
between this species and some of its allies, and a /afa mutant from 
O. biennis has been reported by Gates and described under the 
name of O. biennis mut. lata. Besides O. biennis, some allied 
species also are now known to show the phenomenon of mutation. 
Among these, an American form of O. biennis, which I cultivate 
under the preliminary name of O. biennis Chicago, has been studied 
more extensively than any other form. I had already found in 
the neighborhood of Courtney, Miss., in 1904, in a locality called 
“the bottom,” along the shores of the Missouri River, a single 
* specimen with narrow, almost linear leaves. Evidently it con- 
stituted a wild mutation from the surrounding type.” 
Seeds taken from the normal specimens of this locality have 
since produced in my garden two mutations, which proved, in 
their progeny, to give constant and uniform strains and which 
I have cultivated during a series of years under the names of 
*s Stomps, Tu. J., Parallele Mutationen bel Leena biennis Ber. Deutsch. 
Bot. Gesells. 32:179-188. 1914; also Parallel tions in Oenothera beat L. Amer. 
Nat. 48:494-497. 1914. 
Eecaametde meses pp. 300-301. Berlin. 1913. 
7 OD. cit. 
