472 CUPULIFER^E. (OAK FAMILY.) 



populifolia, Spach.) Poor sandy soils, N. Brunswick to Del., west to L. 

 Ontario. Bark much less separable than the next ; leaves on slender peti- 

 oles, tremulous as those of the aspen. 



4. B. papyrifera, Marshall. (PAPER or CANOE BIRCH. WHITE 

 BIRCH.) Leaves ovate, taper-pointed, heart-shaped or abrupt (or rarely wedge- 

 shaped) at base, smooth and green above, pale, glandular-dotted, and a little 

 hairy on the veins beneath, sharply and unequally doubly serrate, 3-4 times 

 the length of the petiole. (B. papyracea, Ait.) Rich woodlands and stream- 

 banks, N. Eng. to N. Peiin., N. 111., and Minn., and far north and westward. 

 Tree 50-75 high, with bark freely splitting into paper-like layers. Var. 

 MINOR, Tuckerman, is a dwarf form of the alpine region of the White Mts. 



* * * Tree, with greenish-brown bark, somewhat laminate, and reddish twigs, 



ovate leaves whitish beneath, and soft-downy peduncled fruiting catkins. 



5. B. nigra, L. (RIVER or RED BIRCH.) Leaves rhombic-ovate, acutish 

 at both ends, irregularly doubly serrate, whitish aud (until old) downy under- 

 neath; petioles and peduncle of nearly the same length (3-7") aud with the 

 oblong catkin tomentose ; the bracts with oblong-linear nearly equal lobes ; 

 fruit broadly winged. Banks of streams, Mass, to Fla., west to Minn., E. 

 Kan., and Tex. Tree 50 -75 high, with light-colored wood and somewhat 

 Alder-like leaves. 



* * # * Shrubs, with brownish bark, rounded or wedge-shaped crenate and mostly 



small leaves qfthtckish or coriaceous texture, and oblong or cylindrical gla- 

 brous and 7nostly erect catkins, on short peduncles. 



6. B. pumila, L. (Low BIRCH.) Stems (2 -8 high) erect or ascend- 

 ing, no; glandular; young branches and lower face of young leaves mostly 

 soft-downy; leaves obovate, roundish, or orbicular (6-16" long), pale beneath, 

 veinlets on both faces Jinely reticulated ; wing of the fruit mostly narrower than 

 the body. Bogs,W. Conn, and N. J. to Ind. and Minn., and northward through- 

 out Canada. Leaves usually not at all resiniferous or glandular-dotted. 



7. B. glandulosa, Michx. (DWARF BIRCH.) Steins erect or mostly 

 spreading (1 -4 high), or when alpine procumbent; branchlets glabrous, con- 

 spicuously dotted with res/nous wart-like glands ; leaves roundish wedge-obovate 

 or sometimes orbicular (6-9" long), green and glabrous both sides, less reticu- 

 lated ; fruiting catkins mostly shorter and oblong or -ival ; wing of the fruit 

 narrower than or sometimes equalling the body. High mountains of N. Eug. 

 and N. Y., to L. Superior, and far northward. 



2. ALNUS, Tourn. ALDER. 



Sterile catkins elongated and drooping, with 4 or 5 bractlets and 3 (rarely 

 6) flowers upon each short-stalked shield-shaped scale ; each flower usually 

 with a 3-5-parted calyx and as many stamens; filaments short and simple; 

 anthers 2-celled. Fertile catkins ovoid or oblong; the fleshy scales each 2-3- 

 flowered, with a calyx of 4 little scales adherent to the scales or bracts of the 

 catkin, which are thick and woody in fruit, wedge-obovate, truncate, or 3 - 5- 

 lobed, and persistent. Shrubs or small trees, with few-scaled leaf-buds, and 

 solitary or often racemose-clustered catkins, terminating leafless branchlets or 

 peduncles. (The ancient Latin name.) 



