WILLOW FAMILY 



487 



3. Populus trichocarpa Torr. & Gray. 

 Black Cottonwood. Fig. 1188. 



Populus trichocarpa Torr. & Gray; Hook. Icon. PI. 9: 

 pi. 87S. 185.3. 



The largest tree in the genus, attaining a maxi- 

 mum height of 60-70 m. and a diameter of nearly 

 3 m., branches long, forming a broad open crown, 

 winter buds very resinous, long-pointed, the termi- 

 nal 2 cm. long. Bark ashy gray, deeply fissured on 

 old trunks, 3-6 cm. thick ; leaves 3-5 cm. long, 

 ovate, or on young trees or offshoots often oblong- 

 lanceolate, narrowed to the acute apex, rounded, 

 cordate or sometimes cuneate at the base, iinely 

 crenate-serrate, more or less pubescent when 

 young, becoming glabrous, dark green and shining 

 above, pale and usually glaucous beneath ; petioles 

 2-6 cm. long, terete; stamens 40-60; ovary ovoid, 

 pubescent ; capsu]^ nearly sessile, subglobose, 

 about 4 mm. thick, pubescent. 



Stream banks, Upper Sonoran, Transition and Canadian 



Zones; southern Alaska south on the Pacific Slope to the 



San Bernardino Mountains, California, east to northern 



Idaho. Type locality: Santa Clara River, Ventura County, 



California. 



4. Populus fremontii S. Wats. 



Fremont's Cottonwood. 



Fig. 1189. 



Populus fremontii S. Wats. Proc. Am. Acad. 10: 

 350. 1875. 



Tree attaining 35 m. in height with a 

 trunk 1-2 m. in diameter, branches large and 

 spreading, forming a broad open crown. 

 Winter buds 4 mm. long, ovate, sharp- 

 pointed, with light green scales ; bark 3-5 

 cm. thick, light' gray, becoming furrowed 

 toward the base of old trunks ; leaves 4-7 

 cm. long, deltoid, abruptly sharp-pointed at 

 the apex, truncate or cordate at the base, 

 coarsely serrate-dentate, glabrous or some- 

 what pubescent, bright green on both sur- 

 faces ; petioles flattened laterally, yellowish, 

 4-8 cm. long; stamens 60 or more; anthers 

 dark red; ovary glabrous ; capsule 8-12 mm. 

 long, 3-valved ; pedicels about 3 mm. long. 



Stream banks and bottom lands, mainly Lower Sonoran Zone; Upper Sacramento Valley to northern 

 Lower California, southern Xevada and Arizona. Type locality: Deer Creek, Tehama County, California. 

 A pubescent form in southern California has been named var. pubescens Sarg. 



Populus macdougalii Rose, Smithson. Misc. Coll. 61'=: 1. pi. 1. 1913. This is the tree on the Colorado 

 River delta. It diifers from fremontii in its pubescent twigs and leaves, and smaller (3 mm. wide) fruiting 

 disk, but these are not constant characters, and it is doubtful if the species is distinct. 



2. SALIX* L. Sp. PI. 1051. 1753. 



Creeping shrubs to tall trees, with single bud scales lined with an adherent membrane, usually 

 narrow and short-petioled leaves, and persistent to deciduous large to minute stipules (or these 

 wanting). Aments sessile to pedunculate, erect or spreading, appearing before (precocious), 

 with (coetaneous), or after (serotinous) the leaves; bracts of the aments entire or rarely shal- 

 lowly dentate at apex ; each flower accompanied by 1 or sometimes 2 small glands. Stamens 

 1-10, usually 2 or 5, the filaments distinct or sometimes more or less united. Ovary and capsule 

 2-valved, sessile or short-pedicelled, glabrous or hairy ; style wanting to elongate, entire or 

 bifid; stigmas short to long, entire to divided. 



About 300(?) species, mostly of the north temperate and arctic zones, rare in the tropics and southward. 

 Useful for wood, posts, poles, furniture, whistles, holding stream banks, browse for stock, tanning, 

 medicine, etc. Type species, Sali.v pcntandra L. 



''Text contributed by Dr. Carletox R. Ball, U. S. Department of Agriculture. 



