428 Bktulaceje. 



THE HOP-HORNBEAM. Genus OSTRYA Scop. 



Trees of wide distribution tlirouHiiout the northern hemisphere, with scaly bark, slender 

 terete branehlets and hard rather close-grained wood. Four specits are known, two of which are 

 North American. One of them (O. Knoirltoni Cov.l. as far as known, is found only in the 

 Grand Canyon of the Colorado River in Arizona, and the other is a common tree widely dis- 

 tributed throughout the eastern United States and Canada. 



Leaves open and concave in the bud. more or less plaited on the nearly straight veins. 

 Flowers expanding before the leaves: staminate aments in clusters of a few each with short 

 stalks or sessile, developed the previous season near the ends of the branchlets and naked and 

 conspicuous dui-ing the winter : stamens 3-4, crowded on a receptacle at the base of a broad 

 ovate pointed concave scale longer than the stamens: filaments short, 2-branched, each branch 

 bearing a 1-celled half-anther hairy a( apex; ])istillatc tiowri-s in small loose suberect aments 

 terminating leafy shoots and with larg(> pointed deciduous scales nl the base of each of which 

 are 2 flowers each surrounded with a tubular persistent accrescent involucre: calyx adnate 

 to the ovary ; style 2-branched. Fniit an ovoid flattened pointed nutlet, inclosed in an enlarged 

 pale membranous closed sac formed by the enlarged involucre and these together forming a 

 strobile very much resembling a hop. suspended by a slender stem. 



Osinja is the classical Latin name of the European species. 



For species see pp. 116-111. 

 THE BIRCHES. Gexus BETULA L. 



The Birches constitute a considerable and important part of the fores-ts of the Northern 

 Hemisphere of both the Old and the New Worlds. Althougii a few are shrubby species most 

 of them are large and handsome and often aromatic forest trees, some of excep/tional ornamental 

 value with more or less laminate and resinous bark, very tough slender twigs and copious 

 watery and slightly saccharine sap. 



Leaves serrate, dentate, or sometimes incisely lobed. usually thin, from scaly pointed 

 sessile buds; stipules scarions and fugacious. Floircrs unfolding with or before the leaves; 

 the staminate in pendulous often clustered sessile aments whiili form the previous season and 

 remain erect and naked during the winter at or near the ends of the branchlets and rapidly 

 develop expanding their golden flowers in early spring; scales broad-ovate with the two lateral 

 flowers adnate to their bases; calyx membranous, usually 4-lobed ; slaniens 2 with short 

 2-parted filaments, each filament bearing and anther-cell; pistillate aments small oblong or 

 cylindrical, usually iiediincled, termin.nting short lateral 2-leaved branchh>ts and with closely 

 imbricated 3-lobed iiersisient aiciescent scales; calyx wanting; pistil with compressed sessile 

 ovary and 2 si)rea(ling peisistcnt styles stigmatic at the apex. Fru'tt erect, inclined or 

 pendulous strobiles with thin woody o-lobed scales and 3 laterally winged nutlets to each 

 scale and these with the scales falling away from the central axis of the strobile at maturity. 



Betula is the classical name of the Birch-tree. 



KEY TO THE SPECIES. 

 a Branchlets. etc.. not aromatic: strobiles 



b Cylindrical, with long slender peduncles-: wings broader than nutlet : scales 



c I'ubeseent, lateral lobes iiroad and recurved ; bark not easily separable into layers : 

 leaves with long slender petioles, long acuminate and 



Deltoid, wide and mostly truncated at base, bright green B. populifolia. 



Ovate, mostly rounded or wedge-shaped at base, dull blue-green.. B. coerulea. 

 c' Glabrous with spreading lateral lobes: leaves mostly ovate and rounded at base; bark 



creamy white and separating freely into layers B. papyracea. 



b' Oblong, slender, peduncled, mostly erect and lobes of scales linear-oblong: leaves acute. 



B. nigra, 

 a- Branchlets and inner bark aromatic ; strobiles oblong-ovoid, subsessile, erect ; wings not 

 broader than nutlet ; leaves sharply 

 b Serrate : scales of stobiles short glabrous and with rounded lateral lobes : bark dark 



brown and scaly B. lenta. 



b' Doubly .serrate, scales longer and with oblong lobes ; bark yellow or silvorv and laminate. 



B. lutea. 

 For species see pp. 118-121 and the foUowiuf/: 



Blue Birch, Betula coerulea Blanch. A small tree occasionally .30 ft. in height with 

 trunk 8-10 in. in diameter recently described as found in .southevn' Vermont and northern 

 Maine and may be found elsewhere in New England. It resembles the B. populifolia but 

 is said to differ in having leaves rather ovate in outline, more cuneate at base and with dull 

 bluish green upper surfaces. The bark of trunk is described as being more lustrous and of a 

 l)inkish white color. 



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