SALICACEAE 337 



DICOTYLEDONS. 



Leaves netted-veined. Stem increasing in diameter by an annual layer of 

 wood inside the bark. Flowers with the parts in 4s or 5s, the perianth com- 

 monly differentiated into calyx and corolla, sometimes absent. Embryo with 

 2 cotyledons. 



CHORIPETALAE. 



Calyx usually present, sometimes petal-like. Corolla present or absent, when 

 present consisting of distinct or nearly distinct petals. 



SALICACEAE. WILLOW FAMILY. 



Trees or shrubs of rapid growth, light wood and bitter bark. Leaves simple 

 and alternate, with stipules. Flowers dioecious, borne in catkins, these falling 

 off as a whole, the staminate after shedding the pollen, the pistillate after 

 ripening of the fruit and dispersion of the seeds. Bracts of the catkin scale- 

 like. Calyx and corolla none. Stamens 1 to many. Ovary 1-celled ; stigmas 

 Fruit a 2 to 4-valved capsule, enclosing many seeds furnished with a tuft 

 of hairs at base. Two genera. 



Bibliog. Anderson, N. J., Monographia Salicum (1867). Watson, S., Poplars of North 

 America (Am. Jour. Sci. vol. 15, p. 135, 1878). Bebb, M. S., Eeview of the Willows of 

 California (Bot, Gaz., vol. 16, p. 102, 1891). Eydberg, P. A., Cespitose Willows of Arctic 

 America and the Eocky Mts. (Bull. N. Y. Bot. Gard. vol. 1, p. 257, 1899). Eowlee, W. W., 

 North American Willows, Longifoliae (Bull. Ton. Club. vol. 27, p. 247, 1900). Jones, M. E., 

 Willow Family of the Great Plateau (1908). 



Scales entire or merely denticulate, persistent; flowers without disk; stamens usually 1 to 5; 



stigmas short; pods small, ovate or narrow 1. SALIX. 



Scales fimbriate or lacerate, caducous; flowers with a broad disk; stamens usually numerous; 



stigmas elongated or conspicuously dilated; pods larger, nearly globose. .. .2. POPULUS. 



1. SALIX L. WILLOW. 



Trees or shrubs with mostly narrow short-petioled leaves. Winter buds 

 covered by a single scale. Catkins mostly erect, appearing before or with the 

 leaves ; scales entire or merely denticulate, persistent or at least not caducous. 

 Staminate flowers with 1 to 9 stamens and 1 or 2 little glands. Pistillate flowers 

 with a gland at the base of the ovary. Stigmas short. Mainly north temperate 

 and arctic, 160 species. (Ancient Latin name of the willow.) 



Stamens 3 to 9, their filaments hairy or woolly below; style short; stigmas roundish, sub- 

 entire; scales pale or yellowish, in the pistillate catkin more or less deciduous by 

 maturity; capsules pediceled; trees, mainly of lower altitudes. 



Petioles with wart-like glands at summit; leaves lanceolate, long-pointed; stipules usually 

 present, roundish; catkins in bud tapering, in flower usually straight, their scales 



erect 1. S. lasiandra. 



Petioles not glandular; stipules usually absent; catkins in bud cylindric. 



Leaves broadly lanceolate, acute, usually glaucous beneath; staminate catkins curv- 

 ing; scales reflexed or spreading 2. S. laevigata. 



Leaves very narrow, nearly alike on both faces, finely serrulate, often curving towards 



apex 3. S. nigra. 



Stamens 2, their filaments woolly or hairy below; scales pale, somewhat deciduous; catkins 

 borne on short leafy branchlets, often clustered; leaves linear or lanceolate; shrubs 

 of stream beds at lower altitudes. 

 Stigmas linear, raised on a distinct style; ovary densely silky; leaves silvery or green. 



4. S. sessilifolia. 



Stigmas oblong or roundish, sessile. 



Capsule glabrous ; leaves green, remotely serrulate 5. S. longifolia. 



