The willows, which compose one of the most familiar groups of woody plants, 

 line the shores of the rivers and streams, grow in dense stands over moist 

 bottom lands, and frequently abound on the mountain meadows and slopes. 

 Because of their prevalence near routes of travel, places of recreation, and in 

 agricultural and grazing areas these plants are familiar to most people. 



The willows are represented by about 250 species, practically all native to 

 the north temperate and arctic zones ; a few species are confined to the south- 

 ern hemisphere. The name willow is the present form of the ancient word for 

 the genus, which was variously spelled wilowe, welig, wilge. The scientific 

 name Salix, the ancient Latin name of the willow, is probably derived from 

 two Celtic words: sal, near, and Us, water. 



Willows usually grow in moist situations, being commonly associated with 

 fresh water streams and rivers in their natural range. Although they some- 

 times grow "with their feet in the water", they prefer the moist banks, flats, 

 or slopes bordering the very wet sites. They frequent mountain watercourses, 

 often spreading out and forming dense stands on stream bottoms, meadows and 

 other flat areas. A few species, such as Scouler willow (8. scouleria'na, syn. 

 S. nuttal'lii) and Bebb willow (S. bebbia'na), are sometimes common compo- 

 nents of the shrubby vegetation on mountain slopes. The willows seldom 

 grow in the shade ; in fact, most species occur only in full sunlight. 



Willows are found at practically all elevations. The river forms, such as 

 the large black willow (8. ni'gra), frequently thrive on sites only several feet 

 above sea level. A certain few species, including alpine willow (S. petro'phila), 

 appear in the mountains above timber line, and dwarf members of the genus 

 extend as far north as any shrubby plants. Most species, however, limit their 

 ranges to medium and low elevations. 



The majority of willows prefer deep and fertile soils, as indicated by their 

 abundance on river bottoms and meadow lands. Some species, notably the 

 stream types, e. g., arroyo willow (8. lasio'lepis), grow characteristically on 

 rocky stream banks. Scouler willow often inhabits stony soils which, however, 

 are usually fertile enough to support a coniferous forest. Although willows 

 occasionally develop in moist, somewhat acid environments, unlike blueberries 

 (Vaccinium spp.), they cannot endure strongly acid soils and are even less 

 tolerant to alkaline or saline conditions. 



Willows run the gamut in size from the 100-foot, lumber-producing black 

 willow of the lower Mississippi Valley to the almost herblike, high-altitude, 

 and northern species which are less than 6 inches in height. Several of the 

 common western species, e. g., peachleaf willow (8. amygdaloi'des), western 

 black willow (8. lasiari dra) , and red willow (8. laeviga'ta), grow into trees 

 from 40 to 50 feet in height. However, most members of the genus that 

 occur in the mountains, including silverleaf willow (8. argophyl'la), narrow- 

 leaf willow (S. exi'gua,), Lemmon w,illow (8. lem'nwni), and Bebb willow, are 

 distinctly shrubby in character; they range from 3 to 12 feet high and have 

 numerous, crowded, rather long, slender, and few-branched stems which have 

 extended, nodding, leafy tips. 



The deciduous,, short-stemmed, alternate, simple leaves of willows are gen- 

 erally long, narrow, or taper-pointed, with the margins entire or weakly toothed. 

 However, there are many variations in leaf shape, size, surface, texture, and 

 color occurring within the genus, and in some cases within the species or even 

 on individual plants. The tendency of willows to produce hybrids, and the 

 fact that they often flower before the leaves appear, causes much confusion. 

 Another complication obtains, because the leaves often vary greatly in shape, 

 color, and pubescence during their development. 1 One peculiarity, for example, 

 hinges on the fact that a leaf may emerge gray and densely soft-hairy, yet at 

 maturity be green and sparingly hairy or bald. An additional difficulty encoun- 

 tered in the determination of critical specimens of willow is the dioeciousness 

 of the genus, i. e., the sexes are distinct, and sometimes it is necessary to have 

 both the male and female plant represented to be positive of the species. 



The accompanying illustrations present four of the commonest and most 

 characteristic types of leaf form found in willows. The general outline of the 

 long and taper-tipped leaf of tail-leaf willow (8. cauda'ta) is rather charac- 

 teristic of the larger \vestern willows. The narrowly elliptic leaf of Bebb 



1 Ball, C. R. NOTES ON SOME WESTERN WILLOWS. Acad. Sci. St. Louis, Trans. 9 : 

 69-90. 1899. 



