530 EVOLUTION 
The mutations involved various kinds of characters. One of 
the new forms, Oenothera brevistylis, had, among other distinc- 
tive characters, a much shorter style than the Oenothera La- 
marckiana. Another new form, Oenothera laevifolia, had smooth 
leaves and much prettier foliage than the parent type, and its 
petals were not notched. One of the finest and rarest of the 
mutants was the Oenothera gigas (Fig. 473), which was stronger, 
bigger, and more heavily built than the parent. Others of the 
new forms differed from 
the parent in other char- 
acters. 
As to what a new form 
is, can be determined only 
by breeding it and its 
parents in pedigree cul- 
tures. A new form may 
result from crossing be- 
tween two parents with 
different characters and, 
therefore, be a hybrid. 
The new form may be 
due to the fact that the 
parent is a hybrid or de- 
scendant of a hybrid and 
consequently does not 
breed true, thus producing 
offspring different from 
J 
Fic. 473.—The Giant Evening Prim- the parent type. If the 
rose (Oenothera gigas), one of the mutants 
from Lamarck’s Evening Primrose. After pakerts aun pure, amd the 
De Vries. new form is not a hybrid, 
it must be a mutant or a 
fluctuating variant. If it breeds true, it is a mutant; other- 
wise, it is a fluctuating variant. 
By growing the parents of the new forms in pedigree cultures 
for a number of generations, he found that they bred true, 
except for the new forms which occasionally appeared, and 
concluded that the parents were pure. Since the parents of 
the new forms were carefully pollinated artificially, so as to 
prevent crossing between parents differing in characters, the new 
forms were not the result of hybridizing. They were either 
