486 



SALICACEAE 



Family 25. SALICACEAE. 



Willow Family. 



Trees or shrubs with simple deciduous alternate stipulate leaves. Flowers dioeci- 

 ous, in terminal aments, appearing with or before the leaves, maturing in a few 

 weeks and the entire ament falling ofif as a single flower. Each flower subtended by 

 a scale-like bract, without a perianth and with or without a cup-shaped glandular 

 disk. Stamens 2 to many, rarely 1. Ovary 1-celled, ovoid or globose ; stigmas 2— k 

 Fruit a 2-4-valved capsule, with numerous minute comose seeds. 



Two genera, widely distributed, but most abundant in the north temperate and subarctic regions. 

 Bracts fimbriate, caducous; flowers on a cup-shaped disk; stamens numerous; buds with several imbricated 



scales. 1. Populus. 



Bracts entire or merely toothed, persistent or tardily dehiE:cent; disk reduced to a gland; stamens 2-3, rarely 



1 ; buds with a single scale. 2. Salix. 



1. POPULUS L. Sp. PI. 1034. 1753. 



Trees with soft usually whitish wood, resinous buds, terete or angled branchlets, broad or 

 narrow usually petioled leaves and minute fugacious stipules. Bracts of the flowers fimbriate 

 or incised, narrowed at the base. Disk cup-shaped, oblique, lobed or entire. Staminate aments 

 pendulous ; stamens 12-60, or rarely reduced to 4, their filaments distinct. Pistillate aments 

 pendulous, erect or spreading; ovary sessile; style short; stigmas 2-4, entire or 4-lobed. Cap- 

 sule 2-4-valved. Seeds with long copious coma. [Ancient Latin name.] 



About 30 species widely distributed over the northern hemisphere. Type species, Populus alba L. 



Capsule oblong-conical, thin-walled; stigmas 2, 2-lobed, their lobes slender; buds slightly resinous. 



1. P. tremuloides. 

 Capsule globose or oblong-globose, thick-walled; stigmas 2-4-lobed, their lobes dilated; buds conspicuously 

 resinous. 

 Petioles terete; leaves dark green on the upper surface, glaucous beneath. 



Ovary glabrous; petiole glabrous. 2. P. balsamifera. 



Ovary and capsule tomentose; jietioles usually pubescent. 3. P. trichocarpa. 



Petioles strongly flattened laterally; leaves broadly deltoid, bright yellow-green on both surfaces. 



4. P. fremontii. 



1. Populus tremuloides Michx. 

 American Aspen. Fig. 1186. 



Populus tremuloides Michx. Fl. Bor. Am. 2: 243. 1803. 

 Populus vaiicouveriana Trel. ; Tidestr. in Piper & Beattie, Fl. 



N. W. Coast 118. 1915. 

 Populus tremuloides vancouveriana Sarg. Bot. Gaz. 57: 208. 1919. 



Tree with a maximum height of 30-35 m., and a trunk 

 4-6 dm. in diameter, branches slender, often drooping. 

 Bark smooth and greenish white, becoming fissured at 

 the base of old trunks; leaves 3-5 cm. long, broadly ovate 

 to nearly orbicular, crenate-serrate with small incurved 

 glandular teeth except at the shallowly cordate to cuneate 

 base, dark green above, pale yellow green beneath ; 

 petioles slender, laterally flattened, about equalling the 

 leaves; aments 3-6 cm. long; bracts 3-S-lobed, fringed 

 with long hairs; stamens 6-12; stigma lobes linear; cap- 

 sule conical, 3 mm. long, glabrous. 



Borders of streams, lakes and meadows, throughout the 

 Canadian Zone of North America; Labrador to the Yukon, south 

 to Pennsylvania, Missouri, Arizona and northern Lower Cali- 

 fornia. Type locality: Canada and New England. The western 

 plants have been segregated out as a species or variety by some, 

 but the characters used to distinguish the two seem trivial and 



inconstant. 



2. Populus balsamifera L. 



Balsam Poplar. Fig. 1187. 



Populus balsamifera L. Sp. PI. 1034. 1753. 



Tree attaining a maximum height of 35 m. and a 

 diameter of 2 m., with stout erect branches forming a 

 comparatively narrow crown ; winter buds saturated 

 with balsam, the terminal 25 mm. long. Bark on old 

 trunks gray, 20-25 mm. thick, divided into broad 

 rounded ridges ; leaves 7-10 cm. long, ovate to ovate- 

 lanceolate, tapering to an acute or acuminate apex, 

 rounded or narrowed at the base, rarely subcordate, 

 finely crenate-serrate, firm in texture, dark green and 

 shining above, pale green or brownish beneath; 

 petioles terete, slender, 2-5 cm. long; aments long- 

 stalked; stamens 20-30; stigmas much dilated; ovary 

 glabrous ; capsule oblong, 2-valved, 3 mm. long, on a 

 slender pedicel 3 mm. long. 



Low ground near streams and lakes, Canadian Zone; Lab- 

 rador to the Alaskan coast, south to New York, Michigan, 

 South Dakota, Wyoming, Idaho and eastern Oregon. Type 

 locality: eastern North America. 



