1915] DE VRIES—OENOTHERA BIENNIS 173 
primroses are of pure or of hybrid origin is not of paramount 
importance for the appreciation of the fact of their mutability. 
The first attacks on the gametic purity of the mutating forms 
have been directed only against O. Lamarckiana, and at the present 
time the most prominent adherents of this opinon are Davis and 
RENNER. They try to give proof of a separate hybrid nature 
for this species on considerations which do not apply to O. biennis 
‘and the other mutating forms, and concede for these latter a pure 
origin.4 
Davis based his arguments upon a historical research con- 
cerning the origin of O. Lamarckiana, and upon his attempts to 
duplicate this form by crossing others which he assumed to be of 
pure line.’ A specimen collected by MicHavx in the eastern part 
of the United States, about a century ago, and studied by L. 
BLARINGHEM, proves our plant to have been a component of the 
flora of this country, whence Lamarck obtained the authentic 
specimen for his original description.® 
RENNER studied the empty seeds of O. Lamarckiana, which 
constitute over one-half of the whole crop. He brings this phe- 
nomenon in connection with the ability of this species to produce 
twin hybrids, /aeta and velutina, in certain crosses with older types, 
and assumes that the sexual cells are one-half potential Jaeta, and 
the other half potential velutina. In the normal fertilization of 
O. Lamarckiana this would produce } laeta, + velutina, and } of 
the hybrid combination JaetaXvelutina. He further assumes that 
in pure condition both the Jaefa and velutina qualities are incom- 
patible with normal development, and that the germs which bear 
them are doomed to die at an early stage, thereby leaving their 
seeds empty. Only the combination JaetaX velutina would be fit for 
further growth, and if we assume that this shows the marks of 
O. Lamarckiana, the constancy of this form would not be in 
* Davis, B. M., Mutations in Oenothera biennis L. Amer. Nat. 47:116. 1913; and 
Parallel mutations in Oenothera biennis. Ibid. 48: 499-501. 1914. 
5’ ————. Some hybrids of Oenothera biennis and O. grandiflora that resemble O. 
Lamarckiana. Amer. Nat. 45:193-233- 1911. 
° BLaRINGHEM, L., L’Oenothera Lamarckiana Ser. et les Oenothéres de la forét de 
Fontainebleau. Travaux de biologie végétale, dédiés 4 Gaston Bonnter. Rev. Gén. 
Bot. 257: 35-50. 1914; see also my article in Bor. Gaz. §7:345-360. pls. 17-19. 1914. 
. 
