certain North American Convallariaceae. 255 
typical eastern forms, indicating that an evolutionary process of some con¬ 
tinuous kind is in progress. 
The variety 5 . stellata var. mollis (Farwell) comb. nov. is said to differ 
chiefly ‘ in having the leaves densely and permanently velvety pubescent all 
over the lower surface’. The specimens cited are from Michigan and the 
Black Hills of South Dakota. This pubescent variation is apparently 
parallel to Maianthemum Canadense var. interius , Fernald, the type of which 
came also from the arid Black Hills region and which differs from the 
species in being densely hirsute on the stems and the lower surface of the 
leaves. This case of a probable mutation which enabled the species to 
extend its range has been referred to elsewhere. 1 
There are eight recognized species of Disporum in North America, the 
remaining species being European or Asiatic. The distribution of the 
American species is roughly as follows: D . lanuginosum , from Ontario to 
Tennessee; D. maculatum , a restricted area in the mountains of Tennessee 
and North Carolina; D. trachycarpum , from the Canadian prairies south to 
Colorado and west to Oregon ; D. Smithii , in the coast ranges from British 
Columbia to northern California; D. oreganum , distribution similar to that 
of D. Smithii , but extending farther inland ; D. trachyandrnm , in the Sierra 
Nevadas from Oregon to middle California ; D. Hookeri , in a restricted area 
of the coast range of middle California ; D. parvifolmniyX&xe , in the Siskiyou 
Mountains of northern California. 
These species are for the most part rather sharply marked. Nearly all 
of them are clearly distinguished from another species by one striking 
difference, accompanied in some cases by other minor differences. The 
nature of these differences is such as experience teaches us might have 
arisen through a single mutation. Furthermore, we are familiar in the 
Oenotheras with mutations in which one character has been markedly 
modified while others are only slightly altered. Thus D. maculatum differs 
from D. lanuginosum chiefly in having somewhat larger flowers, but most 
strikingly in having the perianth segments yellowish white with fine purple 
spots, instead of greenish. 
Again, D. trachycarpum is sharply distinguished from D. lanuginosum 
and all other species in having beautifully reticulated fruits, whereas they 
are glabrous in nearly all other species. D. trachycarpum was considered 
a variety of D. lanuginosum by both Baker and Hooker, and it is by no 
means unreasonable to suppose that a single mutation may have produced 
it, though it differs from D. lanuginosum also in having fewer seeds, and 
stamens as long as the perianth. 
D. oreganum differs from the eastern species in having an entire instead 
of a three-cleft stigma, and from its nearest relative, D . trachycarpum , in its 
ovate (not globose) pubescent or glabrous but smooth (not reticulated) 
1 The Mutation Theory and the Species-concept. Amer. Naturalist, vol. li, 1917, p. 583. 
