STANDLEY — TREES AND SHRUBS OF MEXICO. 161 



Stamens 2. 

 Leaves small or very small, linear or lanceolate, with stomata equally dis- 

 tributed on both surfaces. 

 Aments short, the staminate ones 5 to 13 mm. long, the pistillate ones in 

 fruit 1.2 to 2 cm. long; anthers globose or short-elliptic, about as broad 



as long 7. S. taxifolia. 



Aments longer, or the anthers elliptic and much longer than broad. 

 Ovary glabrous or sparsely pilose; staminate flowers with 2 glands. 



8. S. exigua. 

 Ovary densely sericeous-villous ; staminate flowers with a single gland. 



9. S. thurberi. 

 Leaves large or broad, without stomata on the upper surface; leaves rarely 

 small, the ovary then long-stipitate. 

 Aments appearing in the axils of full-grown leaves, 2 cm. long or shorter. 

 Ovary glabrous or sparsely pilose. 



Branchlets glabrous; leaves glabrous 11. S. mexicana. 



Branchlets tomentose; leaves more or less tomentulose beneath. 

 Leaf buds rostrate, glabrous or sparsely pilose at the apex ; pedicels 



not longer than the bracts 10. S. hartwegii. 



Leaf buds merely acute, villous-tomentulose ; pedicels longer than the 



bracts 12. S. schaffnerii. 



Aments appearing before or with the leaves. 



Aments scarcely 1 cm. long; leaves usually 2 cm. long or less. 



17. S. cana. 

 Aments more than 2.5 cm. long; leaves mostly much more than 2.5 cm. 

 long. 

 Ovary glabrous; stigmas short; filaments glabrous. 

 Leaf blades lanceolnte. oblanceolate, or narrowly elliptic; staminate 

 aments about 12 mm. thick ; bracts obovate, very obtuse or trun- 

 cate 13. S. lasiolepis. 



Leaf blades elliptic or elliptic-lanceolate ; staminate aments 15 to 20 



mm. thick; bracts oblong, acute 14. S. rowleei. 



Ovary villous ; stigmas lanceolate ; filaments pilose at the base. 

 Bracts narrowly lanceolate, acute or short-acuminate. 



15. S. oxylepis. 

 Bracts oblong, obtuse or subtruncate, rarely acutish. 



16. S. paradoxa. 



1. Salix humboldtiana Willd. Sp. PI. 4: 657. 1805. 



? Salix oxypliyUa H. B. K. Nov. Gen. & Sp. 2: 19. 1817. 



Salix stipulacea Mart. & Gal. Bull. Acad. Brux. 10': 343. 1843. 



Salix humboldtiana stipulacea C. Schneid. Bot. Gaz. 65: 7. 1918. 



Veracruz to Colima. Chiapas, and Tabasco. Central America and South 

 America ; type from Peru. 



Large or small tree, sometimes 10 meters high, with a trunk 15 to 30 cm. in 

 diameter. "Sauce." " sauz," " sauz bianco" (Tabasco). 



The Mexican specimens, as well as those from Central America, belong to 

 S. humholdtiana stipulacea. This differs only slightly from the typical form, 

 which ranges from Colombia to Argentina. A form which is possibly a hybrid 

 between this and S. honplandiana is reported from Oaxaca. 



2. Salix nigra Marsh. Arb. Amer. 139. 1875. 



Salix nigra lindheimerii C. Schneid. Bot. Gaz. 65: 9. 1918. 

 Coahuila to Tamaulipas, Sinaloa, and Tepic. Widely distributed in eastern 

 North America. 



