BETULACEAE 273 



Pa. Luzerne, Lackawanna, Monroe and Northampton counties. 

 Tertiary, o: Cretaceous, o: Older Formations, increasing north- 

 ward. Not south of the moraine except in Pa. 1 17-185 days. 

 Sea level-2,000 ft. 



4. B. nigra L. In moist soil along river valleys and in swamps: 



northeastern Mass. to Fla., west through southern N. Y. to 



111., Minn., Neb., Kan., Tex. and Fla. 



N. Y. Reported, but not recently collected from L. I.; S. I. and 



up the Hudson Valley to Dutchess Co., decreasing northward. 

 N. J. Throughout the state, except the pine-barrens, especially in 



the drainage area of the Delaware River. 

 Pa. Monroe, Northampton and Chester counties, presumably in 



the intervening territory. 



Tertiary, common: Cretaceous, o: Older Formations, decreasing 

 northward. 135-204 days. Sea level-1,800 ft. 



5. B. lenta L. Rocky woodlands: Newf. to Ga. and Ala., west 



to Ont., 111. and Tenn. 



Throughout the range, except in the pine-barrens, there wanting; 

 rare on the coastal plain. 



6. B. alleghaniensis Britton. In woodlands: Mass. to Quebec 



and N. Mich., south to N. Y. and Pa., and in the mountains 



to Ga. 



Conx. Throughout, increasing northward. 



N. Y. Bronx and Westchester counties; Highlands of the Hudson, 



increasing northward and westward ; Copake Falls. 

 N. J. Essex, Passaic and Bergen counties, increasing northward. 

 Pa. Luzerne, Monroe and Pike counties. 



Tertiary, o: Cretaceous, o: Older Formations, increasing north- 

 ward. Not south of the moraine. 1 18-187 days. Sea level- 

 2,200 ft. 



7. B. lutea Michx. In deep forests: Newf. to Man., south to 



Mass., Pa. and Wise. 



Confined so far as now known to the high peaks of Greene and 

 Ulster counties, N. Y., at elevations exceeding 2,800 ft.; a region 

 with a growing season of 1 17-123 days; and to the north shore of 

 L. I. Not south of the moraine. 



5. Alnus [Tourn.] Hill 



Leaves not glutinous when mature; native species. 



Leaves prevailingly obovate; shrub or small tree. 1. A. rugosa. 



19 



