460 betulace^e. (birch family.) 



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

 fruit broadly winged. (B. rubra, Michx.f.) — Low river-banks, E. Massachu- 

 setts to Illinois and southward. — A rather large tree, with light-colored wood, 

 and somewhat Alder-like leaves. 

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



small leaves of thickish or coriaceous texture, and oblong or cylindrical glabrous 



and mostly erect catkins, on short peduncles. 



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

 ing, ?wt glandular; young branches and lower face of young leaves mostly soft 

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

 on both faces finely reticulated ; Aving of the fruit mostly narrower than the body. — 

 Bogs, Conn. (Canaan, W. H. Leggett) to N. Jersey and northward. — Leaves in 

 one form resiniferous or glandular-dotted, usually not at all so. — B. Grayii, 

 Kegel, recently characterized on specimens of a shrub introduced from Central 

 Ohio into the Cambridge Botanic Garden, since lost, appears to be only a marked 

 variety or luxuriant form of the present species, with shoots and young leaves 

 beneath more tomentose, and wings of fruit (which are as wide as body in one 

 Michigan specimen of B. pumila) here almost twice as wide! 



7. B. glanduldsa, Michx. (Dwarf Birch.) Stems erect or mostly 

 spreading (1° -4° high), or when alpine procumbent ; branches glabrous, conspic- 

 uously dotted with resinous wart-like glands; leaves roundish wedge-obovate or 

 sometimes orbicular (6" -9" long), green both sides, less reticulated; fruiting 

 catkins mostly shorter and oblong or oval ; wing of the fruit narrower than or 

 sometimes equalling the body. (B. nana, Ed. 2, not of L. A round-leaved 

 alpine form is B. rotundifolia, Spach., and B. Littelliana, Tuckerman.) — High 

 mountains, Northern New England and New York, and shore of Lake Superior 

 and northward. — The resinous-glandular branches chiefly distinguish some of 

 the larger forms from B. pumila, and the small alpine ones from B. nana, L. 

 of Europe : probably they run together. 



2. ALNUS, Tourn. Alder. 



Sterile catkins elongated and drooping, with 4 or 5 bractlets and 3 (rarely 6) 

 flowers under 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 four 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.) 



§ 1. Flowers developed in spring with the leaves; the sterile from catkins which have 



remained naked over winter ; while the fertile have been enclosed in a scaly bud: 



fruit with a conspicuous thin wing, as in Birch. 



1. A. viridis, DC. (Green or Mountain Alder.) Leaves round. 



oval, ovate, or slightly heart-shaped, glutinous and smooth or softly downy 



underneath, serrate with very sharp and closely set teeth, on young shoots often 



