1918] SCHNEIDER—AMERICAN WILLOWS 337 
is true only to a certain degree, and in my opinion the difficulty 
might be settled by regarding the intermediate forms as hybrids. 
Compared with each other, S. brachycarpa is distinguished by 
the denser and shorter, almost tomentose pubescence, the absence 
of stomata in the upper leaf epidermis, the shorter petioles, 
and the denser and shorter aments, especially the staminate 
with their minute globose anthers; while S. pseudolapponum seems 
to be well marked by the looser, almost a little silky-villose pubes- 
cence, the relatively longer petioles, the presence of more or less 
numerous stomata in the upper leaf surface, and by the somewhat 
looser male aments with rather stiff filaments and larger, more 
ellipsoid anthers. In the female aments the differences are often 
less obvious, and the differences given by BALL (1909) and by 
RYDBERG (1917) seem to me not borne out in fact. 
I have seen no material of S. brachycarpa from Utah where the 
type had been collected. The species seems to be abundant in 
central Colorado from the Culebra Range in the south to the Medi- 
cine Bow Mountains in the north, and southern Wyoming, where 
it is frequently met with in the western part of the state and in or 
near the region of the Yellowstone Park, including northeastern 
Idaho and southern Montana. There is also a specimen before me 
from the Wallowa Mountains in southeastern Oregon (Cusick, 
no. 2298). From. northern Montana its range extends in the 
Rockies to about 59° N. lat. and about 122° W. long., while in 
Alberta it occurs east of the Athabasca River through Saskatchewan 
to about 59° N. lat. I also have before me specimens from Churchill 
on the western shore of the Hudson Bay in Manitoba, and from the 
Gaspé Peninsula, which I am unable to separate even as a variety. 
At first sight the eastern forms seem to differ by the relatively 
shorter and broader leaves, the somewhat longer styles, and the 
longer ventral glands, but the same variations can be observed in 
western specimens. The form from Churchill (J. M. Macoun, 
no. 79156 O.), however, needs further observation. An uncertain 
form is represented by no. 74. Hb. H.B. and T. (fr.; N.), named 
S. desertorum var. acutifolia. It differs from the type by foliis sub- 
acutis ad 32:9 mm. magnis et praecipue amentis fructiferis satis 
laxifloris ad 3.5:1 cm. magnis. 
