iQiS] DE VRIES— OENOTHERA BIENNIS l8l 



From these discoveries it was pretty safe to deduce that the 

 pure 0. 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. Stomps cultivated over 900 individuals 

 of the third and fourth generations of a pure Kne, derived from a 

 rosette collected by him in the sand dunes near Beverwyk, Holland, 

 in 1905.''' Among these he found one 0. biennis mut. nanella, one 

 0. biennis mut. semigigas, and also four instances of the pale- 

 yellow variety 0. 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 0. 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 lata mutant from 

 0. biennis has been reported by Gates and described under the 

 name of 0. biennis mut. lata. Besides 0. biennis, some allied 

 species also are now known to show the phenomenon of mutation. 

 Among these, an American form of 0. biennis, which I cultivate 

 under the preliminary name of 0. biennis Chicago, has been studied 

 more extensively than any other form. I had alteady 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 durmg a series of years under the names of 



'5 Stomps, Th. J., Parallele Mutationen bei Oenothera biennis L. Ber. Deutsch. 

 Bot. Gesells. 32:179-188. 1914; also Parallel mutations in OereoiAera 6jc«»w L. Amer. 

 Nat. 48:494-497. 1914. 



=' Gmppenweise Artbildung. pp. 300-301. Berlin. 1913. 



=" Op. cil. p. 304. 



