690 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Leaves pinnate. 



Young branchlets densely pubescent 1. A. serratvun. 



Young branchlets glabrous 2. A. orizabense. 



Leaves simple, lobed. 



Leaves truncate or rounded at base 3. A. mexicanum. 



Leaves cordate at base 4. A, brachypterum, 



1. Acer serratum Pax, Bot. Pahrb. Engler 6:296. 1885. 

 Negundo mexicanum DC. Prodr. 1: 545. 1824. 



Acer mexicanum Pax, Bot. Jahrb. Engler 7: 212. 1886. Not A. mexicanum 

 A. Gray, 1862. 



Tlaxcala, Mexico, Puebla, and Chiapas, and probably elsewhere. Guatemala. 



Tree ; leaflets 3, lanceolate to broadly ovate, 6 to 12 cm. long, long-acuminate, 

 coarsely and irregularly serrate, densely pubescent beneath ; flowers dioecious ; 

 petals none; samaras about 3 cm. long, pubescent. "Acezintle," "acecincle" 

 (Mexico); " arce." 



2. Acer orizabense (Rydb. ) Standi. 



Negundo orizabense Rydb. Bull. Torrey Club 40: 55. 1913. 



Veracruz, Mexico, and Michoacjin ; type from Orizaba, Veracruz. 



Tree, the young branches green ; leaflets 3, lanceolate, ovate, or rhombic-oval, 

 5 to 15 cm. long, acute or acuminate, serrate, soon glabrate l)eneath ; petals 

 none; samaras 3.5 to 4 cm. long. 



This is closely related to A. negundo L., the box-elder of the United States, 

 and may not be distinct. 



3. Acer mexicanum A. Gray, Proc. Amer. Acad. 5: 176. 1862. 

 Described from Nuevo Leon. 



Leaves dilatate-cuneate and 3-lobed or 5-lobed, about 5 cm. broad, the lobes 

 sinuate, glabrate ; flowers polygamous ; samaras glabrate, the wing 1.5 to 

 2 cm. long. 



4. Acer brachypterum Woot. & Standi. Contr. U. S. Nat. Herb. 16: 146. 1913. 

 Mountains of Chihuahua and Sonora ; type fi-om San Luis Mountains. South- 

 ern New Mexico. 



Tree, 18 meters high or less, the trunk sometimes 70 cm. in diameter, witli 

 spreading crown ; leaves 5-lobed, 6 to 8 cm. wide, paler beneath and velutinous, 

 the lobes sinuate or entire; samaras glabrate, the wings about 1.5 cm. 

 long. 



This is closely related to A. grandidentatum Nutt., of the western United 

 States and may be only a form of that species. The leaves turn red in autumn. 



88. AESCTJLACEAE, Horse-chestnut Family, 



Trees or shrubs; leaves opposite, estipulate, digitately 3 to 9-foliolate, the 

 leaflets serrate or entire ; flowers paniculate or racemose, terminal, polygamous, 

 irregular ; calyx 5-lobed ; petals 4 or 5, unequal, clawed ; stamens 5 to 8 ; fruit 

 a coriaceous capsule, subglobose or 3-lobate, usually 3-celled; seeds one in 

 each cell. 



Calyx lobed nearly to the base; leaves persistent; leaflets 3 1. BILLIA. 



Calyx lobed to the middle or less deeply ; leaves deciduous ; leaflets usually 



5 or 7 2. AESCULUS, 



1. BILLIA Peyr. Bot. Zeit. 16: 153. 1858. 

 1. Billia hippocastanum Peyr. Bot. Zeit. 16: 153. 1858. 

 Aesculus mexicana Benth. & Hook. ; Hemsl. Biol. Centr. Amer. Bot. 1 : 212, 



1880. 

 Veracruz and Oaxaca ; type from Oaxaca. 



