352 Tlie New York State College of Forestry 



family includes but two genera, Salix comprising the willows and 

 osiers, and PopiUus, the aspens and cottonwoods. 



Leaves alternate, deciduous, simple, stipulate (stipules often caducous). 

 Flo Iters dioecious, without perianth, borne solitary in the axils of scales in 

 axillary aments which appear before the leaves in spring; staminate flowers 

 consisting of 1-many stamens, inserted on a receptacle, subtended by a gland- 

 lite or cup-shaped disk; anthers 2-celled, longitudinally dehiscent; pistillate 

 flowers consisting of a pistil wdth a 1-celled ovary surmounted by a short style 

 and 2— i-lobed stigma; ovules numerous. Frmt a 1-celled, 2-4-valved, ovoid 

 capsule bearing numerous, comose, minute, exalbuminous seeds. 



KEY TO THE GENERA page 



1. Scales of the ament entire; disk minute, glandular; buds with a single scale .... 



Salix 352 



2. Scales of the ament laciniate; disk cup-shaped; buds with numerous scales. . . . 



Populus 3")3 



THE WILLOWS. Genus SALIX (Tourn.) L. 

 The genus Salix includes about one hundred and seventy 

 moisture-loving species of trees and shrubs, widely scattered 

 throughout the northern hemisphere, a few forms occurring south 

 of the equator. They thrive along stream banks and on moist 

 bottom lands, and invade alpine summits and subarctic regions 

 as scraggly, dwarfed shrubs. Approximately seventy species occur 

 in North America, twenty-one of which are recognized as trees. 

 A number of European species have been introduced for ornament 

 and have become widely naturalized in eastern United States. 

 Hybrids between European and native species are common. 



Leaves alternate, simple, lanceolate to linear or obovate, short-petioled; 

 stipules conspicuous oblique, serrate and persistent, or small and caducous. 

 Flowers dioecious, borne in aments, with entire bracts and minute, gland-like, 

 neetiferous disk; staminate flowers consisting of 1-12 stamens (generally 

 2 or 5) inserted at the base of the scale, with slender, mostly free filaments 

 and small, oblong anthers; pistillate flowers consisting of a sessile or short- 

 stalked, 1-celled ovary surmounted by a short style and 2-cleft or entire, more 

 or less curved stigmas; ovules numerous. Fruit an acuminate capsule open 

 ing by 2 recurved valves, maturing in late spring or early summer; seeds 

 minute, comose, exalbuminous. Winter huds covered with a single scale. 



KEY TO THE SPECIES page 



1. Stamens 1-2 .2 



1. Stamens 3 or more (generally 5) 7 



2. Capsules glabrous 3 



2. Capsules silky or tomentose 5 



3. Mature leaves with pale silky pubescence on both sides 



S. alba, var. vitellina 117 



3. Mature leaves glabrous or essentially glabrate .4 



4. Branches long and drooping; capsules sessile S. babylonica 11!) 



4. Branches not drooping; capsules short pedicelled S. fragilis 1 1 5 



