160 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



10. Populus macdoug'alii ^ Rose, Smiths. Misc. Coll. 61": 1. 1913. 



Northern Sonora and Baja California ; type from the delta region of the 

 Colorado River. 



Large tree; differing from P. fremontii only in the more copious pubescence, 

 and probably not spwifically distinct. 



2. SALIX L. Sp. PI. 1015. 1753. 

 Reference: C. Schneider, Bot. Gaz. 65: 1-41. 1918. 



The various species of willows are found in nearly all parts of Mexico, 

 usually growing at the edge of water. They are often planted as shade trees. 

 Salix babylonica L. ("sauz llor6n," the weeping willow), an Old World species, 

 with very long, slender, drooping branches, is sometimes cultivated also. 



The wood is used chiefly for firewood, but also for construction to a limited 

 extent. In the United States it is burned for charcoal, which is of excellent 

 quality, being used in medicine and as black crayon by artists. The bark is 

 sometimes used for tanning, and the leaves as forage for stock. The flexible 

 tough branches are employed for making baskets, and they were so used by 

 many tribes of North American Indians. They are used also in Mexico as 

 well as elsewhere in the manufacture of wicker furniture. The bark and leaves 

 contain tannin and salicin. The latter principle is a useful febrifuge, and was 

 widely used before quinine came into general use. A willow decoction is still 

 employed for treating fevers in Mexico in domestic practice, and other medicinal 

 properties are attributed to the plants. 



The usual names for species of Sallx are " sauz " and " sauce." The follow- 

 ing ones are said to be applied to species which have not been determined by 

 the writer: "Ahuejote " (Jalisco, Valley of Mexico); " huejocote," " huexotl " 

 (Nahuatl) ; " tepehuexote " ("Valley of Mexico); " yaga-gueza " (Zapotec) ; 

 " yutnu-nuu " (Oaxaca, Mixtec, Rcko). 

 Stamens 3 or more. 

 Leaves glaucous or glaucescent beneath. 



Branchlets yellow or yellowish, glabrous 4. S. wrightii. 



Branchlets reddish or purplish or tomentulose. 

 Branchlets densely tomentose ; leaves densely villous-tomentulose beneath 

 when young; petioles 8 mm. long or less; staminate aments O.S 



to 3 cm. long 5. S. jaliscana. 



Branchlets glabrous or sparsely pilose; leaves glabrous beneath or nearly 

 so; petioles mostly over 10 mm. long; staminate aments 4 to 6 cm. 



long 6. S. bonplandiana. 



Leaves green beneath. 

 Branchlets yellowish or yellowish cinereous ; ovary often pilose. 



3. S. goodding'ii, 

 Branchlets reddish or purplish ; ovary glabrous. 



Capsule ovoid to elliptic, scarcely attenuate or short-atteninite at the 

 apex; leaf blades linear or linear-lanceolate; stipules eglandular. 



1. S. humboldtiana. 

 Capsule ovoid-lanceolate, attenuate at the apex; leaf blade.'; linear-lan- 

 ceolate to broadly lanceolate ; stipules glandular on the inner surface. 



2. S. nigra. 



^ Named in honor of Dr. D. T. MacDougal (1865-), director of the de- 

 partment of botanical research of the Carnegie Institution, distinguishetl for 

 his contributions to the knowledge of plant physiology. Dr. MacDougal has 

 made limited collections of plants in Mexico, some of which are in the U. S. 

 National Herbarium. 



