4l'8 Bj-:tl'i,ac'£\e. 



THE HOP-HORNBEAM. Genus OSTRYA Scop. 



Trees of wide (listiil)U(iiiii lliiouKhout the noi'tlieni hemispliere, with sealy bai'l':. slemlei- 

 terete branclilets and liard rather elose-gi-aiued wood. Four specits aie luiowii, two of whieli are 

 Xortli Ameriran. (hie of tliem ( O. K iioirltoiii Cov. ) , as far as known, is found only in tlie 

 (Jrand Canyon of the Colorado Uiver in Arizona, and the other is a cpmmon tree widely dis- 

 tributed tlu-oughout the eastern United t^tates and Canada. 



Leaccx open and eoneave in tlie bud, more or les.s plaited on the nearly straight veins. 

 Floivrrs e.xpanding before the leaves ; staminate araents in elustei-s of a few each with shmt 

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

 conspicuous during the winter; stamens 3-4, crowded on a receiitaide at the base of a bi-oail 

 ovate pointed concave scale longer than the stamens; filaments short. 2-branched, each bramli 

 bearing a l-celled half-anther hairy at apex; pistillate flowers in small loose suberect anieiits 

 terminating leafy shoots and with large pointed deciduous scales at the base of each of which 

 are L! flowers each surrounded with a tubular persistent accrescent involucre; calyx adnate 

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

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

 strol)ile very much resembling a hop. suspended by a slender stem. 



(Jxti-iiu is the classical Latin name of the European species. 



For aprcics sec pp. 116-111'. 



THE BIRCHES. Genus BETULA L. 



The Birches constitute a considerable and important part of the forests of the Northern 

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

 of them ar(> large and handsome and often aromatic forest trees, some of excepjtional ornamental 

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

 watery and slightly saccharine sap. 



Lrai-rx serrate, dentate, or sometimes incisely lobed, usually thin, from scaly pointed 

 sessile buds; stipules scarious and fugacioits. Floicerii unfolding with or before the leavi's ; 

 the starninate in piendnlous often clustered sessile aments which form the previous season and 

 remain erect and naked during the w-inter at or near the ends of the branehlets and ra])idly 

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

 flowei-s adnate to their bases; calyx membranous, usually 4-lobed ; stanaens 2 with short 

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

 cylindrical, usually peduncled. terminating short lateral 2-leaved branehlets and with closely 

 imbricated 3-lobed persistent accrescent scales; calyx wanting; pistil with compressed sessile 

 ovary and 2 spreading persistent styles stigmatic at the apex. Frnit erect, inclined or 

 pendulous strobiles with thin woody 3-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 Bi'anchlets, etc., not aromatic; strobiles 



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



o Pubescent, lateral lobes broad and recurved ; bark not easily separable into layers : 

 leaves with long slender petioles, long acuminate and 



I'eltoid, wide and mostly truncated at base, bright green B. populifolia. 



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

 e^ 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- Branehlets 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 silvery and laminate. 



B. lutea. 

 For xprcicf see pp. llS-127 and the foUoirinr/: 



Blue Bikcii, Betula cwrulea Blanch. A small tree occasionally .30 ft. in height with 

 trunk .S-10 in. in diameter recently described as found in southern Vermont and northern 

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

 liinkish white color. 



