498 " CXXV. BETULACE^. Betula, 



1. BETtJLA. Tourn. 



Bctu ia the Celtic name for the birch. 



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

 stamens 10 — 12. 9 Ament oblong-ovoid: scales subtrilobate ; calyx 

 ; nut compressed, with a membranaceous margin. — Trees and shrubs 

 mostly with the outer bark laminated and horizontally fibrous. Lvs. 

 ovate., serrate, alternate. 



* Trees. 



1. B. LENTA. Black Birch. Sweet Birch. Mahogany Birch. 



Dvs. cordate-ovate, acuminate, acutely serrate, veins beneath and petioles 

 hairy; fertile aments erect. — This noble species is common in the Eastern and 

 Middle States, often exceeding 60f in height, with a diameter of 2 to 3f. The 

 trunk is invested with a dark brown or reddish bark, which becomes rough in 

 old trees, and is remarkable for its agreeably aromatic fragrance and flavor. 

 Leaves 3 — 4' long, about J as wide. Sterile aments 2 — 3' long, fertile much 

 shorter and thicker. In spring the cambium affords the boys a delicious morsel. 

 The wood is of a reddish color, strong, compact, and takes a good polish. It 

 is much used in cabinet work. April, May. 



2. B. ExcELSA. Ait. Lofty or Yellow Birch. 



Lvs. ovate, acute, serrate, on pubescent petioles, shorter than the pedun- 

 cles ; barren aments ovate, erect ; scales with rounded, lateral lobes. — A common 

 forest tree in N. England, arising in woods to the height of 60 — 80f, with a 

 trunk 2 — 3f diam., invested with a thin, yellowish cuticle. Barren aments 2 — 

 4' long, cylindric, clustered, and pendulous at the ends of the branches. The 

 wood is chiefly valuable as fuel. April, May. 



3. B. NIGRA. Ait. (B. rubra. Michx.) Bed Birch. 



Lvs. rhombic-ovate, acute at each end, doubly serrate, glaucous beneath ; 

 fertile anient sessile, erect, ovoid, scales villous, the segments linear, equal. — A 

 tree 30 — 50f high, growing on the banks of streams, Methuen, Mass., Emersmi, 

 to Car. W. to la. ! and III, Mead. Trunk covered with a reddish or chocolate- 

 colored bark, which at length becomes very loose and torn, hanging in shreds, 

 and finally rough like that of the black cherry. Branches arched and slender ; 

 branchlets almost filiform, often clothing the trunk to the base. Leaves dark 

 green above, about 3' by 2', often smaller, petioles 6 — 8" long, pubescent. May. 



4. B. POPULIPOLIA. Ait. Poplar-leaved Birch. White Birch. 



Lvs. deltoid, long-acuminate, unequally serrate, very smooth, on smooth 

 petioles; fertile aments pedunculate; scales with roundish, lateral lobes. — This 

 species, like the preceding, is distinguished for the white cuticle with which the 

 trunk is invested. It is common in the rocky and mountainous woods of N. 

 England, where it seldom exceeds 30 — 40f in height. The branches are covered 

 with a reddish-brown bark, very slender, and throw out, in May, long, pendu- 

 lous aments. 



5. B. PAPYRACEA. Ait. Paper Birch. Canoe Birch. 



Lvs. ovate, acuminate, doubly serrate, the veins hairy beneath ; fertile 

 aments nodding, pedunculate ; lateral lobes of the calyx short, roundish. — This 

 birch is abundant in the hillside woods of N. England, &c. It sometimes at- 

 tains the height of 60 — 70t, but is generally smaller. The trunk, which is I — 

 2f in diameter, is covered with a tough cuticle consisting of numerous lamina, 

 the outer of which is snow white. Of this the Indians construct their light 

 canoes. The bark upon the branches is dark brown. Leaves 2 — 3' long, J as 

 wide. Sterile aments 1 — 2' long. The wood is of a fine, compact texture, but 

 not durable, and is used in turnery and furniture work. May, June. 



/3. minor. Tuckerman. Lvs. smaller, ovate, glabrous, acute, some of them 

 roundish-obtuse. — White Mts. Shrubs 6 — 9f high. 



* Shrubs. 



6. B. puMii.A. Dwarf Birch. 



Low, shrubby ; yomig branches pubescent, without glandular dots ; lvs. or- 

 bicular-obovate, petioles dense!}' pubescent beneath ; fertile ament cylindrical. 



