KEY TO THE SPECIES OF ALDERS 



1. Buds sessile, 3-6 scaled, dark purple; pistillate ament enclosed 

 in bud during winter; leaves ovate, lobulate, usually irregularly 



singly toothed; Alaska to California and east to Montana 



Alnus sinuata (Reg.) Rydb., Sitka Alder, p. 161. 



1. Buds stalked, 2-3 scaled; pistillate anient appearing in fall (some- 

 times enclosed during winter in red alder). 



2. Leaves with 8-15 pairs of veins. 



3. Leaves lobulate, doubly toothed; buds reddish. 



4. Wing of nut broad; leaves ovate to elliptic, often red- 

 hairy below, slightly revolute; important tree; Alaska to 



California and east to Idaho 



Alnus rubra Bong., Red Alder, p. 159. 



4. Wing of nut reduced to narrow border; leaves neither 

 red-hairy nor revolute ; shrubs or rarely small trees to 30 

 feet. 



5. Twigs marked with orange lenticels; Rocky Moun- 

 tains and Pacific Coast from Yukon to Mexico 



Alnus tenuifolia Nutt., Thinleaf Alder, p. 161. 



5. Twigs marked with white lenticels; Newfoundland 

 to Saskatchewan, south to Pennsylvania and Nebraska, 



also in Europe and Asia 



. . .Alnus rugosa (D. R.) Spr., Speckled Alder, p. 161. 



3. Leaves finely to coarsely toothed. 



6. Western shrubs or smzill trees; leaves coarsely toothed. 



7. Leaves oval or ovate; Idaho to Washington and south 



to lower California 



Alnus rhombifolia Nutt., White Alder 



7. Leaves oblong-lanceolate; New Mexico and Arizona, 



south into Mexico 



Alnus oblongifolia Torr., Arizona Alder 



6. Eastern shrubs, rarely small trees; leaves finely toothed. 



8. Leaves with straight veins; several pistillate catkins 

 per bud; Maine to Minnesota and south to Florida 

 and Texas. . .Alnus serrulate (Alt) Willd., Hazel Alder 



8. Leaves with arching veins; 1-3 pistillate catkins per 



bud; Delaware, Maryland, and Oklahoma 



Alnus maritima (Marsh.) Muhl., Seaside Alder 



2. Leaves with 5-6 pairs of veins, oval to orbicular, coarsely and 

 doubly toothed; native to Eurasia but naturalized in the 



Northeastern States 



Alnus glutinosa (L.) Gaertn., European Alder 



[157] 



