162 American Midland Naturalist Monograph No. 4 



Field Guidl to the Species 



Leaves deciduous; shrubs found in parks other than in Sierra Nevada. 



Leaves mostly 3 to 5 inches long; occurs in parks of the Northwest 



1 . R. PuTshiana. 



Leaves mostly less than 3 inches long; shrubs found east of Great Western 

 Divide. 



Winter buds enclosed by small bud scales; flowers usually 2 to 5 in the 



leaf-axils; found in northern parks 2. R. alnifolia. 



Winter buds without bud scales; flowers usually in clusters of 5 to 12; 



found in the Southwest 3. R. beiulaefolia. 



Leaves evergreen ; shrubs of the Sierra Nevada parks. 



Leaves mostly more than 1 inch long, the margins not spine-toothed; berries 

 black when ripe. 



Stems red; leaves thinnish, % to 1 J/2 inches long, mostly rounded at the 



tips 4. R. rubra. 



Stems grayish or brownish; leaves thickish, 2 to 3 inches Icng, mostly 



pointed at the tips 5. R. iomentella. 



Leaves mostly less than 1 inch long, the margins spinose-loothed and holIy-like; 



berries red 6. R. crocea var. ilicifolia. 



L Cascara Sagrada Buckthorn {Rhamnus Purshiana DC). — Shtoib 

 or small tree 8 to 20 feet high with leaves in bunches at the ends of the branch- 

 lets; bark gray; leaves elliptic-oblong, 21/2 to 5 (or 8) inches long, thinnish, 

 blunt-pointed at the tip, the margins usually finely and rather irregularly 

 toothed; flowers small, greenish, borne on slender stems in small clusters in 

 the leaf-axils; berries black, about Y^ to 1/3 inch in diameter, usually 3-seeded. 

 The plants favor moist shaded places in the forests. The common name, 

 cascara sagrada, meaning sacred bark, is derived from the fact that the bark 

 is commonly used medicinally. The berries are eaten by certain birds and 

 small mammals and the foliage is of some importance as a browse for 

 mule deer. 



Occurrence. — OLYMPIC, 400 to 2,000 feet: Lake Crescent; Lake Quinault; En- 

 chanted Valley. MOUNT rainier, rare. CRATER LAKE, occasional, 4,500 to 6,500 feet: 

 Annie Creek at south entrance; near park headquarters; Castle Crest; Pole Bridge; 

 south of Whitehorse Bluff; lower Red Blanket Creek. 



2. Alder Buckthorn (Rhamnus alnifolia L' Her.), fig. 94. — Small 

 shrub 2 to 6 feet high; leaves elliptic, 1 to 3^/2 inches long, more or less pointed 

 at both ends, thin, smooth, prominently veined, the margins toothed; flowers 

 greenish, inconspicuous, borne singly or 2 to 5 on slender stems in the leaf 

 axils; berries black, I/4 to 1/3 inch in diameter, 3-seeded, the nutlets flattened 

 on one side; occurs along streams and in wet places. 



Occurrence. — GLACIER, occasional, 4,300 feel to timberline: Avalanche Lake; Swift- 

 current Lake and Valley; Kintla Lake; Waterton ranger station; Crossley Lake; Two 

 Medicine valley; Red Eagle Lake; St. Mary Lake and Valley. YELLOWSTONE: Ob- 

 sidian Creek. GRAND TETON: Jackson Lake. ISLE ROYALE, occasional at edges of bogs: 

 near Lake Desor; Washington River. 



3. Birch Buckthorn (Rhamnus betulaefolia (Greene) var. obovata 

 Kearney & Peebles) . — Spreading shrubs 3 to 6 feet high, the young branches 



