(259) 
The work 1s based on specimens in the following herbaria: 
Columbia University, New York Botanical Garden, Geolog- 
ical Survey of Canada, Harvard University, Messrs. Wil- 
liam M. Canby, Frank Tweedy, and my own. 
To draw a line between the cespitose and fruticose willows 
is, of course, impossible. I have tried to confine myself to 
those that are usually less than half a meter high. There 
are several species from the Cascades and Sierra Nevada 
that might have been included here, but as my knowledge of 
these is so limited, I have omitted them. 
The arctic or alpine willows may be grouped as follows: 
Capsule more or less one tomentose or villous. 
tyle almost n RETICULATAE. 
Style evident. ARCTICAE. 
Capsule glabrous or nearly so. 
Leaf margin entire. 
Leaves 1-2 cm. long; catkins many-flowered; style generally evi- 
VALIFOLIAE. 
t, but short. 
Leaves less than 5 mm. long; catkins few- (in ours 2-4-) flowered ; 
style almost none. RETUSAE. 
Leaves serrate or dentate. HERBACEAE. 
RETICULATAE. 
Densely cespitose arctic or alpine willows with mostly 
prostrate branches and less than 1 dm. high (except S. 
vestita) ; leaves rather thick and more or less reticulate (ex- 
cept S. glaczal’s) ; ovary more or less tomentose, with a ses- 
sile twice 2-cleft stigma. 
Leaves covered beneath with long white silky hairs. 1. S. vestita. 
Leaves at least in age not silky beneath 
Leaf-blade over 1 cm. long. 
Lower portion of filaments very hairy; leaves ree reticulate. 
cts prone obovate, fuscous, almost a abro at least the 
s 
upper portion. : es 
Bracts von lea densely hairy. . S. reticulata, 
Filaments almost glabrous; leaves less strongly reticulate; bracts 
cuneate-oblong, a. almost glabrous. 4. S. saxtmontana. 
Leaf-blade I cm. long or less. 
es few-flowered, less than 1 cm. long; leaves strongly reticu- 
; bracts yellow, almost Jagan 5. S. utvalis. 
Pee many-flowered, 1-3 cm. long; leaves thin, not reticulate; 
bracts fuscous, hairy. 6. S. glacialis. 
