72 SALICACEAE (WILLOW FAMILY) 



W. Steins ascending, 30-90 cm. high; leaves long-hairy beneath, 3-4.5 cm. long, 

 2-3.5 cm. wide, obscurely crenulate; aments 3-3.5 cm. long. E. S. vestita 

 WW. Stems creeping, 3-10 cm. high; leaves glabrous beneath, 0.7-2.5 cm. 

 long, 0.4-1.5 cm. wide, entire; aments 1-2 cm. long. 

 X. Leaves 15-25 mm. long, 10-15 mm. wide; aments 1-2 cm, long, many- 

 flowered. C. S. saximontana 

 XX. Leaves 7-12 mm. long, 4-8 mm. wide; aments 0.5-1 cm. long, 3-6- 

 flowered. C. S. nivalis 

 KK. Aments on leafy peduncles, 

 Y. Shrubs 1.5 m. or less high (except S.lemmoni, S. barclayi, and S. macrostachya); 

 ament scales wider than linear, obtuse or acute, brown or gray-brown or black, 

 not reddish at tip; capsule peduncle 2-5 mm. long. 

 2. Stipules present, rather large on vigorous shoots (except 5. wolfii); stigma entire. 

 a. Leaves lanceolate; scales of aments black. E. S. lemmoni 

 aa. Leaves either ovate-lanceolate or else widest at or above the middle of the 

 blade; scales of aments not black. 

 b. Leaves glabrate above, glabrous and glaucous beneath, crenate or serrulate. 

 W. C. E. S. barclayi (barclay willow) 

 bb. Leaves quite hairy on both sides, not glaucous beneath. 

 c. Stipules large, ovate. W. C. E. S. commutata 

 cc. Stipules small or none. 

 d. Twigs ash-colored, hairy; pistillate aments 2.5-5 cm. long. E. 



S. macrostachya 

 dd. Twigs yellow-brown, glabrous; pistillate aments 1-2.5 cm. long. C. E. 



S. wolfii 

 ZZ. Stipules none or very small; stigma not entire. 

 e. Erect shrubs, bog plants, alpine or low-land, 4 dm. or less high; mature leaves 

 mostly 3-6 cm. long. W. C. E, S. myrtilloides (bog willow) 



ee. Depressed or creeping shrubs, rock plants, alpine, less than i dm. high ; 

 mature leaves mostly 1-3 cm. long. 

 f . Leaves 2-4 cm. long, pale beneath, broadly elliptic to obovate. E. 



S. petrophila (rock willow) 

 ff. Leaves 1-1.2 cm. long, deep green or slightly pale beneath, narrowly ellip- 

 tic to obovate. C. S. tenera (small-leaved willow) 

 YY. Shrubs 2-5 m. high; ament scales linear-oblong, acute, tawny, reddish at 

 tip; capsule peduncle 0-1.5 mm. long. 

 g. Leaves elliptical-oval; peduncle of ament 2-5 mm. long; twigs without bloom. 

 E. S. bebbiana (bebb willow) 

 gg. Leaves linear-oblanceolate; peduncle of ament 1.5-2.5 mm. long; twigs with 

 bloom. W. E. S. geyeriana (geyer willow) 



POPULUS (Poplar) 



Trees; bud scales resinous. Leaves wide, petioled; stipules minute, 

 fugaceous. Disk cup-shaped, oblique. Staminate aments dense, pendu- 

 lous ; stamens 6-40. Pistillate aments sometimes raceme-like : ovary 

 sessile; style short; stigmas 2-4, entire or 4-lobed. Seed hairs often very 

 long and conspicuous. — (L. popuhis = the common people ; planted in 

 public places by the Romans.) 



A. Petiole strongly flattened laterally. 

 B. Tree not strikingly narrow for its height; branches spreading, their angle with 

 the stem more than 45°; leaves ovate to suborbicular, short-pointed. W. E. 



P. tremuloides (aspen) 



