26o 



The Alders 



Trees or shrubs flowering in early spring. 



Nut bordered by a broad membranous wing on each margin. 

 Nut acutely margined or narrowly winged. 



Foliage not glutinous when mature; native species. 



Leaves prevailingly obovate; eastern shrub or small tree. 

 Leaves ovate, oval or ovate-lanceolate; seldom obovate. 



Leaves mostly brown-pubescent beneath, at least upon the veins; 

 Pacific coast tree; stamens 4; staminate catkins i to 1.5 dm. 



long- 

 Leaves green beneath. 



Leaves smooth or somewhat hairy beneath; western trees 

 and shrubs. 

 Leaves obtuse, rounded or cordate at the base, doubly 

 serrate or somewhat lobed; stamens 4; staminate catkins 

 3 to 6 cm. long. 

 Leaves mostly narrowed, cuneate or acute at the base, 

 serrate, not lobed; stamens i to 3, usually 2. 

 Leaves ovate to oval, obtuse or acute; Pacific coast 



tree. 

 Leaves oblong to oblong-lanceolate, acute or acumi- 

 nate; southwestern tree. 

 Leaves densely hairy on the veins beneath; eastern shrub or 

 small tree. 

 Foliage glutinous; introduced European tree. 

 Autumn-flowering; eastern tree. 



I. A. fruticosa. 



2. A. serrulata. 



3. A. rubra. 



4. A. tenui folia. 



5. A. rhombi folia. 



6. A. oblongifolia. 



7. A. noveboracensis. 



8. A. rotund if olia. 



9. A. maritima. 



Fig. 218. Northern Alder. 



I. NORTHERN ALDER - 

 Alnus fruticosa Ruprecht 



This tree has long been confused 

 with the shrubby Green alder, Alnus 

 Alnohetula (Ehrhart) K. Koch, of 

 northern Europe and northeastern 

 North America, with which it agrees 

 in having the nut bordered by broad 

 membranous wings, but it forms a 

 tree up to 12 meters in height or 

 more, with a trunk at least 2 dm. in 

 diameter. 



It occurs in eastern Siberia, 

 Alaska, and the Yukon Territory. 

 The American tree has been separa- 

 ted from the Asiatic one by Professor 

 Sargent under the ndjne Alnus sitchen- 

 sis, but our studies indicate that the 

 two are not specifically different. 



