254 BIRCH FAMILY 



In bogs and tamarack swamps, common throughout the north half 

 of the state, and as far south as Minneapolis and St. Paul, rare and local 

 farther south, in Goodhue, Olmstead and Houston counties. Distributed 

 from Newfoundland to western Ontario, south to N. J., 111., and Minn., 

 also Europe and Asia. Flowers in May, fruit ripe in July and August. 



Betula pumila var. glandulifera Re gel 1865 



Differs from the species in that the young branchlets and leaves are 

 resiniferous or glandular-dotted. 



Northwestern .part of the state. Distributed from Ontario and Mich, 

 to Minn, and Saskatchewan. 



Alnus Gaertner 1791 Alder 

 (Latin name of the alder) , 



Shrubs or trees with dentate or serrate leaves and few-scaled buds ; 

 flowers in catkins, appearing the preceding season and expanding before 

 or with the leaves, staminate flowers 3 or 6 in the axil of each bract, 

 perianth of four parts, stamens 4, the 2 outer flowers subtended by 1-2 

 bractlets each, pistillate flowers 2 or 3 in the axil of each bract, perianth 

 lacking, 2 small bractlets subtending each flower, ovary 2-celled, styles 2, 

 in fruit the bracts become woody and 5-toothed or pointed and together 

 form a cone-like structure, nutlet flattened, with or without wings. 



A genus of about 14 species, natives of the northern hemisphere and 

 the Andes Mountains of South America. In addition to the following, 

 some 6 or 7 species occur in North America. 



Key to the Species 



1. Leaves finely serrate, resinous beneath when 



young, nutlets with a membranous wing A. crispa 



2. Leaves coarsely serrate, not resinous, nutlet 



acute-margined, wingless A. incana 



Alnus crispa (Aiton) Pursh 1814 Green or Mountain Alder 

 Alnus alnobetula (Ehrhart) K. Koch 1872 



A shrub 0.6-3 m. high, bark gray or brownish, young shoots brownish, 

 more or less pubescent and glutinous; leaves ovate or oval, rounded at 

 the base, obtuse or acute at the apex, finely, sharply and often irregularly 

 serrulate or incised-serrate, dark green and glabrous above, lighter green 



