472 cupuLiFER^. (oak family.) 



populifoHa., 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.) Leaces 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 X. Penu., 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, icith greenish-brown bark, somewhat laminate, and reddish twigs, 



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



5. B. nigra, L. (River or Red Birch.) Leaves rhombic-ovate, acutish 

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

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

 oblong catkin tomentose ; the bracts with oblong-linear nearh' equal lobes; 

 fruit broatlly winged. — Banks of streams, Mass. to Fla., Avest 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 mosthj 



small leaves ofthickish or coriaceous texture, and oblong or cylindriccd gla- 

 brous and mostly erect catkins, on short peduncles. 



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

 ing, not glandular ; young branches and lower face of young leaves mostly 

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

 veinlets on both faces finely 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.) Stems erect or mostly 

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

 spicuously dotted with resinous 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 )val ; wing of the fruit 

 narrower than or sometimes equalling the body. — High mountains of N. Eng- 

 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.) 



