254 SALICACEiE. 



A very large genus of shrubs and trees, growing chiefly along water- 

 courses in the northern temperate zone, but some inhabit high mountains, 

 and one is found nearer the north pole than any other shrubby plant. All 

 known species are bitter, and contain salicin in a greater or less proportion. 

 The one in which this principle is most abundant, and which has therefore 

 been chiefly employed medicinally, is : 



Salix alba Linne. — White Willow. 



Description. — Catkins long, loose, pedunculate, borne on the summit of 

 the lateral leafy branches of the season. Scales entire, greenish-yellow, 

 more or less hairy, falling before the pods are ripe. Stamens mostly 2 ; 

 filaments hairy below. Ovary short-stalked or nearly sessile, glabrous; 

 stigmas thick, recurved. 



A tr:e, 50 to 80 feet high. Leaves lanceolate or elliptic-lanceolate, 

 pointed, somewhat toothed, clothed more or less with white, silky hairs, 

 especially beneath. 



Habitat. — Introduced from Europe, but naturalized and very common 

 in moist situations. 



The indigenous species of willow are very numerous, and many of them 

 are very common, but, as few of them have ever been employed medicinally, 

 they need not occupy our attention here. 



Part Used. — The bark of salix alba and of other species of salix. — i 

 United States Pharmacopoeia. 



Constituents. —Willow bark contains as its most important constituent, 

 salicin. This, as remarkecl above, has been found in all species which have 

 been examined. On this account the Pharmacopoeia recognizes not only 

 salix alba, but "other species." The bark also contains considerable tan- 

 nin, and common vegetable principles. 



Preparations. — None are official. It has been employed in powder, de- 

 coction, and infusion. The active principle, salicin, is the most eligible 

 and efficient form in which to employ it. 



Medical Properties and Uses. — Willow bark is tonic and antiperiodic. It 

 has been used in intermittents, and as a tonic in dyspepsia, debility, and 

 convalescence. Recently salicin has been employed with asserted benefit in 

 rheumatism. 



POPULUS. —Poplar. 



Character of the Genus. — Scales of the catkins jagged or irregularly cut- 

 lobed at the apex. Flowers in a cup-shaped disk ; the staminate with 4 to 

 30 stamens ; the pistillate of a single pistil. Trees w T ith broad, more or 

 less cordate leaves, the petioles often compressed laterally, thus occasion- 

 ing a tremulous motion when the least agitated. Catkins long and droop- 

 ing, appearing before the leaves. 



Populus tremuloides Michaux. — American Aspen. 



Description. — Scales of the catkins in 3 or 4 linear divisions, fringed 



