648 Order 120.— BETULACE^E. 



dulous; buds rather acute. — A small tree disseminated throughout the TJ. S., 

 25 — 30f in height. Its bark is remarkable fur its fine, narrow, longitudinal di- 

 visions. Leaves about twice as long as wide. The l'ruit is similar in appearance 

 to hops, suspended from the ends of the branches, consisting of membranous, im- 

 bricated sacs (cups?) containing each a flower. The wood is very white, hard 

 and strong, much used for levers, &c. Apr., May. 



6. CARPFNUS, L. Hornbeam. (Celtic car, wood, and pino, the 

 head ; alluding to its use in making yokes for cattle.) <$ Flowers in a 

 long, cylindric anient; cal. scale roundish, clliate ; sta. 8 — 14, slightly 

 bearded at summit. $ Flowers in a loose anient ; scale large, oblong, 3- 

 lobed, 1 — 3-flowered ; cal. 6-toothed ; stig. 2; nut long, ovoid, fur- 

 rowed, 1-seeded. — Small trees. Scales of the $ aments persistent and 

 becoming foliaceous. 



G. Americana L. Lvs. oblong-ovate, acuminate, unequally serrate ; scales of the 

 fertile ament 3-parted, the middle segment much the largest, oblique, with a 

 lateral tooth. — A small tree (12 — 20f high), common in woods throughout the U. 

 S. The wood is very fine-grained, compact and white, covered with a light gray 

 or ash-colored bark. Leaves 2 — 4' long, £ as wide, petiolate. From the ends of 

 the branches hang the long, loose, pale green, leafy aments, consisting of alter- 

 nate pairs of enlarged scales, with a dark-colored nut at the base of each. Apr, 

 May. 



Order CXX. BETULACE^E. Birchworts. 



Trees or shrubs with deciduous stipules. Bark separating into thin layera. Leaves 

 alternate, simple, with the veinlets running straight to the margin. Flowers mon- 

 oecious, amentaceous, mostly naked, 3 in the axil of a 3-lobed bract. I Stamens 

 definite, distinct. Anthers 2-celled. $ Ovary 2-celled, 2-ovuled, becoming in fruit 

 1-celled and 1-seeded (by abortion) membranous and indohiscent. Seed pendulous, 

 without albumen. Figs. 17, 90, 106, 111, 419, 420. 



Genera 2, upecien 65, chiefly natives of tho cool parts of tho northern hemisphere. Properties 

 generally astringent. The birches are often fine timber trees. 



i. BE'TULA, Tourn. Birch. (Betu is the Celtic name for the birch.) 

 3 Flowers in a cylindric ament ; bracts deeply 3-parted, peltate ; calyx 

 a scale ; stamens 4. $ Ament oblong-ovoid, scales trilobate ; calyx ; 

 ovaries 3 under each scale ; stigmas 2, filiform ; nut compressed, with 

 a membranous margin. — Trees and shrubs, with the outer bark lam- 

 inated and horizontally fibrous, the inner aromatic. Branchlets dot- 

 ted. Lvs. ovate, serrate. Figs. 419, 420. 



* Trees with a yellowish bark, smoothish leaves, and short, erect, ? aments No. 1 



* Trees with a reddish-brown bark and ovate-oblong, suberect, 8 aments Nos. 3, 3 



* Trees with a white bark, lung-stalked leaves and drooping % aments Nos. 4, 5 



* Shrubs with brownish bark, roundish leaves and short, erect, ? uinents Nos. 6, 7 



1 B. excelsa Ait Yellow Birch. Lvs. ovate-elliptic, subacuminate ; sub- 

 cordate, coarsely, sharply, and doubly serrate, smooth when old, on short, downy 

 petioles ; fertile amenta erect, ovoid-oblong ; lobes of the bracts subequal, acute, 

 diverging. — A common forest tree, N. Eng. to Mich, and Can., arising in woods 

 to the height of GO to 80f, with a trunk 2 to 3f in diam., invested with a thin. 

 yellowish, silvery outer bark stripping off in transverse shreds. Barren aments 

 2 to 4' long, cylindric, clustered, and pendulous at tho ends of the branches ; 

 fertile 1' long, 6" diam. Apr., May. 



2 B. lenta L. Black Birch. Sweet Birch. Mahogany Birch. (Fig. 202.) 

 Lvs. cordate-ovate, acuminate, acutely, finely, and doubly serrate, veins beneath 

 and petioles hairy; fertile aments erect, oval-oblong, thick, obtuse, pedunaUate; 

 icales hairy, the lobes obtuse, subequal, diverging. — This noble species is com- 

 mon in tho Eastern and Middle States, often exceeding 60f in height, with a 



