114 
IOWA ACADEMY OP SCIENCE 
Baxter in his British Phanerogamous Botany, in 1839, gives a plate 
(4:257) which seems to resemble 0. Lamar cliiana rather than 0. grandi- 
flora. But doubtless 0. grandiflora from its first introduction from 
Virginia ( ?) had escaped from English gardens long before the later 
introduction in 1778, and was growing wild -as we now find it, mingled 
with 0. Lamar cMana forms. This figure may therefore refer to some 
hybrid between the two.^ It is referred to as 0. biennis, the only English 
species. 
Dietrich, in characterizing 0. grandiflora Ait. in the German flora 
(Gaertnerei und Botanik 6:202) in 1837, describes the leaves as smooth 
and the capsules as ^‘filzig. ” The style is described as ^‘so lang als die 
Staubfaeden.’’ The liairiness of the capsule and especially the short style 
make it not improbable that he was describing hybrids between 0. bien- 
nis and 0. grandiflora. 
After the time of Linnaeus, the large-flowered Oenotheras are fre- 
quently referred to and figured as 0. biennis, and in England this prac- 
tice has continued down to the present time. It is justified, as we have 
seen, by Linnaeus’ citation of figures in his characterization of the 
species. But in America, where these large-flowered species have long 
been rare or absent, usage has tended to confine the term to a small- 
flowered self-pollinating form, and this is what is meant when the name 
0. biennis L. is used in the present paper. Thus a plant is figured under 
this name by Sowerby (English Botany 22 pi. 1534) in 1806, and he 
says ‘‘Our specimen was gathered on the extensive and dreary sand- 
banks on the coast a few miles north of Liverpool, where millions of the 
same species have been observed ... perfectly wild, and covering 
a large tract between the first and second range of sand-hills.” The 
plate has large flowers and answers to 0. Lamarckiana rather than to 
0. grandiflora (See plate 6). However, at this date 0. grandiflora was 
also doubtless naturalized in the same locality, where my cultures have 
shown that the two species are intercrossing freely, and the plant 
figured in Sowerby undoubtedly represents one of many such races 
growing together in that locality. As already mentioned, some 0. grandi- 
should point out that treating such intermediate races as possible hybrids does 
not in the least explain their origin from an evolutionary standpoint. Just as there 
is no such thin«’ in nature as a sharply defined Linnaean “species,” but rather a 
host of m_ore or less independent elementary species which, in open-pollinated forms, 
are continually intercrossing- so that the lines of descent are chang-ing- with each 
generation ; so there is no sharp line between a hybrid and a pure form. By self 
pollinating during successive generations, the individuals will be found to breed true 
to smaller and smaller differences, except when mutations occur. If such “pure” indi- 
viduals are then pollinated from some other race, no one can say how closely or 
distantly that race should be related to produce a hybrid rather than a “pure” strain. 
In na.ture, except in strictly self-fertilized forms, the indiscriminate crossing of indi- 
viduals exhibiting a host of minute character differences, is the normal condition. 
The process of separating and purifying races by self-pollination is analagous to the 
chemical process of fractional crystallization. 
