BETULACEAE (BIRCH FAMILY) 835 



S. B. nigra L. (River or Red B.) Tree with greenish-brown somewhai 

 iR,mmate bark and reddish twigs ; leaves acutish at both ends, when v<nin" 

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

 bracts with oblong-linear nearly equal lobes. — Banks of streams and in swunn.s 

 e. of the Alleghenies from e. Mass. to Fla., thence w. to Tex.; and throu-h the 

 bottom-lands of the Mississippi R. system. ° 



* * Trees or shrubs loith slender cylindric fruiting catkins, their scales readily 

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

 prominetit veins. '' 



w Wing distinctly broader than the body of the fruit ; trees or stout shrubs with 

 white, whitish, or brown papery bark. 



«. Bark dull, chalky- or ashy-white, smooth and close, the layers not readily 

 exfoliating ; staminate catkin usually solitary. 



4. B. populif5Iia Marsh. (White, Gray or Old Field B.) Trunk usually 

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

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

 both sides, except for the resinous glands when young, tremulous on \ery slender 

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

 the drab or ashy-brown wide-spreading scales 2.5-4 mm. long, the'w lobes puheru- 

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

 to L. Ont. ■ ' * 



•w. 4H. Bark lustrous, creamy- or pinkish-white to bronze, freely splitting into 

 paper-like layers; staminate catkins mostly 2 or 3. 



= Branchlets and leaves strictly glabrous from the first. 



5. B. p^ndala Roth. (White or Canoe B.) Branches slender and flexuous, 

 often drooping, the branchlets usually verrucose with resiniferous atoms ; leaves 

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

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

 pendulous, 1.5-3 cm. long, 6-9 mm. thick ; the ascending brown or stravj-colorea 

 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.). 



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



pubescent beneath. 



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

 ing ; resiniferous atoms, if present, mixed with long hairs ; leaves ovate, taper- 

 pointed, from rounded to cuneate at base, in maturity 3-6 cm. long, smooth and 

 green above, pale, glandular-dotted, and a little hairy on the veins leneath, sharply 

 and unequally double-serrate; fruiting catkins 1.5-4.5 cm. long, 0.5-1.6 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. to N. E., the Great Lake region, etc. (Eurasia.) 

 Passing to the commoner American 



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

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

 Neb., Wyo., and Wash. 



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

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

 Valley, Me. (Eu.) 



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

 veins 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, ghitinous, glabrous, 1.5-4 cm. long; staminate catkin ofte/i soli- 

 tary ; fiTiiting catkins mostly ascending, 1 .3-3 cm. long, 0.5-1 cm. thick. iR 



