MUTATION IN THE EVENING PRIMROSE 529 
the fuzz of a peach, sometimes arises as a branch of the Peach 
tree. 
Mutation in the Evening Primrose. — The Evening Primrose 
is especially noted because it has furnished much of the material 
upon which the mutation theory is founded. One of the diff- 
culties in finding mutations is that any given species does not 
mutate all of the time but only at occasional periods. In 
1886 De Vries began to search for species that were in the 
mutating period. The 
American Evening Prim- 
rose (Oenothera Lamarck- 
tana) (Fig. 472), also 
known as Lamarck’s 
Evening Primrose, proved 
to be the species for which 
he was searching. He 
found a large number of 
plants of this species 
growing in an abandoned 
potato field at Hilversum, 
near Amsterdam. Among 
them he found some un- 
known and very distinct 
forms which apparently 
had come from seeds of 
the normal American 
Evening Primrose. Seeds 
were secured from the : ; ; 
Fig. 472. — Lamarck’s Evening Primrose 
normal plants, and cul- (Oenothera Lamarckiana), a mutating 
tures were begun in the species. After De Vries. 
Botanical Garden at the 
University of Amsterdam. From the first sowing he obtained 
another new form. Through a series of pedigree cultures in- 
volving a number of generations, quite a number of distinct 
forms were obtained. Some of these distinctly new forms ap- 
peared repeatedly in the cultures, while others appeared only 
once, but they all bred true, thus producing offspring like them- 
selves. These new forms did not arise gradually but appeared 
suddenly and were so distinct from the American Evening 
Primrose, their parent, as to be called new species. 
‘ ~s 
