168 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Mature strobiles 20 mm. long or longer. 

 Petioles pubescent. 

 Leaf blades broadly rounded at the base, broadly elliptic-ovate. 



3. A. pringlei. 

 Leaf blades acute or acutish at the base, ovate or oblong-ovate. 



4. A. oblong'ifolia. 

 Petioles glabrous. 



Leaves conspicuously pilose beneath, at least on the nerves. 



5. A. arguta. 

 Leaves glabrous beneath or nearly so 6. A. glabrata. 



1. Alnus jorullensis H. B. K. Nov. Gen. & Sp. 2: 27. 1817. 



Along streams, Jalisco to Veracruz and Oaxaca ; type from Volcjin de 

 Jorullo, MichoacSn. Guatemala. 



Shrub or tree, 3 to 6 meters high or larger, with smooth, reddish brown 

 branches; leaves oblong or obovate, 7 to 13 cm. long; strobiles 1 to 2 cm. long. 



2. Alnus firmifolia Fernald, Proc. Amer. Acad. 43: 61. 1907. 



State of Mexico; type from Cima Station, at an altitude of 3,000 meters. 

 Tree, 6 to 12 meters high. 



3. Alnus pringlei Fernald, Proc. Amer. Acad. 43: 62. 1907. 



Type from Uruapam, Michoacan ; perhaps also in Durango and Jalisco. 

 Small tree. "Aliso " (Durango). 



Certain doubtful forms are intermediate between this and A. oblongifolia, 

 but the type collection appears distinct from the latter species. 



4. Alnus oblongifolia Torr. U. S. & Mex. Bound. Bot. 204. 1859. 



Sonora ; perhaps also in Durango and Tepic. Southern New Mexico (type 

 locality) to southern California. 



Small or medium-sized tree, sometimes 10 meters high, with a triuik 2-5 cm. 

 in diametei-, the branches reddish brown; bark thin, light brown; leaves 5 

 to 10 cm. long ; catkins 9 cm. long or shorter ; strobiles 1 to 1.5 cm. long. 



5. Alnus arguta (Schlecht.) Spach, Ann. Sci. Nat. II. 15: 205. 1841. 

 Betula arguta Schlecht. Linnaea 7: 139. 1832. 



Alnus arguta cuprca Bartlett, Proc. Amer. Acad. 44: 610. 1909. 



Alnus arguta subsericca Bartlett, Proc. Amer. Acad. 44: 610. 1909. 



Tamaulipas to Veracruz (type locality), Oaxaca, and Chiapas; apparently 

 also in Chihuahua. 



Tree, 6 to 7.5 meters high, the branches brown ; leaves ovate or obovate, 4 to 

 10 cm. long ; strobiles 2 to 8 cm. long. 



The Chihuahua specimens were referred doubtfully to A. glabrata by Bart- 

 lett, but seem essentially the same as A. arguta. This species has been referred 

 to A. acuminata H. B. K., A. fcrruginea H. B. K.. and A. jorullensis castaneac- 

 folia (Mirb. ) Regel, none of which is known to occur in Mexico. 



6. Alnus glabrata Fernald, Proc. Amer. Acad. 40: 20. 1904. 



Alnus glabrata clurangensis Bartlett, Proc. Amer. Acad. 44: 611. 1909. 



Hidalgo to Oaxaca ; Durango ; type from Monte San Nicolfis, Guanajuato. 



Large or medium-sized tree ; leaves oblong-lanceolate or elliptic, coarsely 

 dentate, acuminate. "Aliso" (Durango). 



A. glabrata clurangensis Bartlett is a form in which the lower surface of the 

 leaves is glauceseent ; it may be si)eclfically distinct. Specimens of A. glabrata 

 have been reported from Mexico as A. rhombifolia Nutt. 



