BETULACEAE (BIRCH FAMILY) 335 



3. B. nigra L. (Kiver or Red B.) Tree with creenish-brown somewhat, 

 laminate bark and redilish -twiu-s ; leaves acuti.sh at both ends, when young 

 downy underneath ; petioles, peduncles, and thick-cylindric catkins tomentose ; 

 bracts with oblonu:-linear nearly equal lobes. — Banks of streams and in swamps 

 e. of the Alleghenies from e. Mass. to Fla., thence w. to Tex. ; and through the 

 bottom-lands of the Mississippi R. system. 



* * Trees or shrubs xoith slender cylimlric fruiting catkins, their scales readily 

 deciduous ; leaves {of the fruiting branches) with 7 or less pairs of 

 prominent veins. 



A- Wing distinctly broader than the body of the fruit; trees or stout shrubs luith 



lohite, whitish, or brown papery bark. 



•w Bark dull, chalky- or ashy-white, smooth and close, the layers not readily 

 exfoliating ; starninate catkin usually solitary. 



4. B. populif51ia Marsh. (White, Gray or Old Field B.) Trunk iLSually 

 ascending, rarely 10 m. high; leaves triangular (deltoid), very taper-pointed 

 (usually abruptly), truncate or nearly so at the broad base, smooth and shining 

 both sides, except far the resinous glands when young, tremulous on veiy slender 

 petioles ; fruiting catkins slender-stalked, ascending, 1-3 cm. long, 5-7 mm. thick ; 

 the drab or ashy-brown icide-spi-eading scales 2.5-4 ram. long, their lobespubera- 

 jent. — Poor sandy or rocky soil, commonest near the coast, P. E. I. to Del., w. 

 to L. Ont. 



■w- ++ Bark lustrous, creamy- or pinkish-white to bronze, freely splitting into 

 papei'-like layers ; starninate catkins mostly 2 or 3. 



= Branchlets and leaves strictly glabrous from the first. 



5. B. pendula Roth. (White or Caxoe B.) Branches slender and flexuous, 

 often drooping, the branchlets iLSuall}^ verrucose with resiniferous atoms ; leaves 

 glutinous when young, lirm, rhombic-ovate to deltoid or broad-ovate, subcuneate, 

 truncate, or subcordate at base, long-acuminate, slender-petioled ; fertile catkins 

 pendiiloiLS, 1.5-3 cm. long, 6-9 mm. thick ; the ascending brown or straw-colored 

 scales 3-5 mm. long, glabrous except for the ciliate margin. (B. verrucosa 

 Ehrh.) — Rocky upland woods and slopes, Que. to Alaska, locally s. to Me., Vt., 

 111., Man., etc. (Eurasia.) — A polymorphous boreal species, of which the N. E. 

 phase has recently been designated as B. caerulea Blanchard (Blue B.). 



= = Branchlets puberulent or pubescent ; young leaves (except in var. minor) 

 ^ pubescent beneath. 



6. B. alba L. (Paper, Canoe or White B.) Branches and branchlets ascend- 

 ing ; resiniferous atoms, if present, mixed with long hairs : leaves ovate, tai'er- 

 pohited, from rounded to cuneate at base, in maturity 3-0 cm. long, smooth and 

 green above, pale, glandular-dotted, and a little haii^ on the veins beneath, sharply 

 and unequally double-serrate; fruiting catkins 1.5-4.5 cm. long, 0.5-1.5 cm. 

 thick, spreading or drooping on slender peduncles ; the mostly ciliate-margined 

 ascending scales 3-7 mm. long. (B. pubescens Ehrh.) — Large shrub or medium- 

 sized tree, Nfd. to B. C, s.1io N. E., the Great Lake region, etc. (Eurasia.) 

 Passing to the commoner American 



Var. papyrifera (Marsh.) Spach. Usua,lly a larger tree, with mature leaves 

 6-9 cm. long. (B. papyrifera Marsh.) —Nfd. to Alaska, s. to Pa., lad., u. la.. 

 Neb., Wyo., and Wash. 



Var. glutin5sa (Wallr.) Trautvetter. Branches pendulous ; leaves 3-5 cm. 

 long, pilose on the veins beneath ; catkins on straight pfdundes. — Wassataquoik 

 Valley, Me. (Eu.) 



Var. cordif51ia (Regel) Fernald. Leaves broad-ovate, cordate, pilose on the 

 veiiLS beneath. — Cool woods and mts.. Lab. and Nfd. to B. C, s. to N. E., L. 

 Superior, la., and westw. — Becoming a dwarf shrub on alpine slopes. 



Var. minor (Tuckerm.) Fernald^ Stout dwarf shrub; leaves elliptic- or 

 truncate-ovate, glutinous, glabrous. 1.5-4 cm. long; starninate catkin often soli- 

 tary ; fruiting catkins mostly ascending, 1.3-3 cm. long, 0.5-1 cm. thick. CB. 



