202 FAGAOEAE 



white and punctate beneath, with many lateral veins and obsolete reticulations, 

 usually entire or with a few spinulose-tipped teeth; those of the sterile shoots 

 almost orbicular or round-ovate in outline, coarsely and deeply dentate with 

 spinose-tipped teeth; cup hemispheric, 10-14 mm. in diameter; scales ovate, 

 with brown acute tips; acorn ovoid, about 15 mm. long. Mountains: N.M. 

 Utah Ariz. Nev. Son. 



17. Q. turbinella Greene. A shrub 1-3 m. high; young branchlets covered 

 with a white stellate-pubescence and when young with fulvous tomentum; leaf- 

 blades oblong, elliptic, oval or rarely ovate, 1-3 cm. long, acute at the apex, 

 usually sinuate-dentate with spinulose-tipped teeth, when unfolding covered 

 with a fulvous tomentum, light bluish green and shining above, strongly reticulate, 

 fulvous, stellate-pubescent beneath; cup 8-10 mm. in diameter; scales deltoid- 

 ovate, obtuse, moderately corky-thickened; acorn 15-20 mm. long, 8 mm. in 

 diameter. Dry hills: Calif. Utah Ariz.; Sonora and L. Calif. Son. Ap-My. 



FAMILY 32. BETULACEAE. BIRCH FAMILY. 



Monoecious trees or shrubs, with simple alternate leaves. Staminate 

 flowers in long drooping aments, each bract subtending 2 or 3 flowers; calyx 

 present. Pistillate flowers also in aments, but the aments seldom drooping, 

 without calyx; pistils 2 or 3 at the base of each bract. Fruiting aments 

 cone-like; fruit small nuts or samaras; seed solitary. 



Bracts of the mature pistillate aments membranous, in ours 3-lobed, deciduous with the 

 fruit. 1. BETULA. 



Bracts of the mature pistillate aments thickened and woody, persistent. 2. ALNUS. 



1. BETULA (Tourn.) L. BIRCH. 



Shrubs or trees, with resinous aromatic bark; branchlets with transverse 

 lenticels. Staminate aments slender, pendulous; calyx irregularly 2- or 4-lobed; 

 stamens 2, inserted at the base of the calyx; filaments very short, branched at the 

 apex; anther-sacs separate. Pistillate aments erect or drooping, oblong or 

 cylindric; bracts elongate, in ours 3-lobed, 3-flowered, accrescent, deciduous. 

 Fruit small, samara-like or nut-like, flat; outer seed-coat thin, produced into a 

 wing or margin ; seeds solitary, pendulous . 



Bark separating into layers or sheets, the very thin outer layer peeling into small shreds; 



all trees. 

 Bark chalky white to silvery gray. 



Leaves broadly ovate, with acute apex, mostly subcordate base, and spreading 

 teeth; twigs mostly glabrous; middle lobe of the bractlets acute, slightly longer 

 than the rounded lateral ones. 1. B. subcordata. 



Leaves narrowly ovate, with long-acute or acuminate apex, rounded or cuneate 

 base, and teeth directed forward; twigs pubescent; middle lobe of the bractlets 

 narrow, rounded at the apex, about twice as long as the acute or obtuse lateral 

 ones. 2. B. papyrifera. 



Bark yellowish or reddish brown, often very dark; twigs very glandular. 



Leaves ovate, very thin, dark green, acute at the apex, irregularly doubly-serrate,. 



with long-pointed, slender teeth. 3. B. occidentalis. 



Leaves deltoid or ovate, thick, bronze-green, long-acuminate at the apex, coarsely 



and more regularly serrate. 4. B. alaskana. 



Bark not separating into layers; outer bark not peeling into shreds. 

 Samara-wing broader than the body. 



Twigs and branchlets glandular-resiniferous, not hairy. 



Lateral lobes of the bractlets spreading, obliquely ovate, auricled at the baser 



trees. 



Leaves very thin; fruiting aments narrowly cylindric, elongate, less than 

 1 cm. thick; lateral lobes of the bractlets obtuse or rounded; claw much 

 shorter than the middle lobe. 5. B. Piperi. 



Leaves thick; fruiting aments broadly cylindric, stout, more than 1 cm. 

 thick; lateral lobes of the bractlets mostly acute; claw as long as the 

 middle lobe. 6. B. utahensis. 



Lateral lobes of the bractlets ascending, obliquely rhombic, not auricled at the 



base; shrubs or trees. 



Shrubs or small shrub-like trees; bark shining, dark red-brown, smooth; 

 leaves broadly oyate, usually less than 4 cm. long, coarsely and irregu- 

 larly serrate, thin, dark green, obtuse or acute at the apex, mostly 

 rounded at the base; twigs densely glandular-resiniferous. 



7. B. fontinalis. 



