64 FAGACEAE 



Cup flat, covering less than one-fourth of the acorn. 



4. Q. Vreelandii. 

 Cup hemispheric, covering one-tliird to one-half of the acorn. 



Mature leaves very thin, glabrate beneath or puberulent only on the 

 veins; cup covering about one-half of the acorn. 



5. Q. leptophylla. 

 Mature leaves flrrn, puberulent beneath; cup covering about one-third 



of the acorn. 

 Leaves mostly oblong in outUne, lobed half way to the midrib or 



less, rather dull. 6. Q. Gunnisonii. 



Leaves obovate in outline, divided deeper than half way to the mid- 

 rib, very shining above. 



Lobes of the leaves broadly oblong, rounded at the apex. 



7. Q. Gambellii. 

 Lobes of the leaves ovate or triangular, acute. 



8. Q. novomexicana. 

 Leaves pale or bluish green, more persistent. 



Leaves broadly obovate, with narrow sinuses. 9. Q. Eastwoodiae. 



Leaves oblong-obovate, or elliptic; sinuses broad. 



Lobes oblong-ovate, obtuse or acutish, not mucronate. 



10. Q. venustula. 

 Lobes triangular-ovate, mucronate. 11. Q. Fendleri. 



Leaves persistent, usually evergreen, entire, sinuate or dentate, or if more deeply lobed, 

 the lobes with spinulose tips. 

 Cup hemispheric; acorns barrel-shaped. 



Scales of the cups decidedly corky-thickened on the back. 



Leaves decidedly crisp, sinuately lobed; lobes distinctly sptnulose-tipped. 



12. Q. pungens. 

 Leaves flat, sinuate-dentate or entire; teeth mucronate, or sometimes slightly 

 spinulose-tipped . 

 Acorns 6-7 mm. tlilck; cup shallow, enclosing about one-third of the acorn; 



leaves usually sinuate-dentate. 13. Q. undulata. 



Acorns about 1 cm. thick or more; cup deeper, enclosing about half of the 

 acorn. 

 Leaves usually entire, except those of the young shoots. 



14. Q. grisea. 

 Leaves lobed, with few (5-7) lobes. 1.5. Q. panciloba. 



Scales of the cups thin, only sUghtly thickened on the back; leaves glabrate and 

 shining above in age. 16. Q. Wilcoxii. 



Cup more or less turbinate; acorns elongated-ovoid. 17. Q. turbinella. 



Family 32. BETULACEAE. Birch Family. 



Bracts of the mature pistUlate ameats membranous, in ours 3-lobed, deciduous with the 

 fruit. 1. Betul.\. 



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



1. BETULA (Tourn.) L. Birch. 



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 roimded lateral ones. 1. B. subcordala. 



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 ver>' glandular. 



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

 with long-pointed, slender teeth. .3. B. occidenlalis. ■ 



Leaves deltoid or ovate, tliick, 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 slireds. 

 Samara-wing broader than the body. 



Twigs and branchlets glandular-resiniferous, not hairy. 



Lateral lobes of the bractlets spreading, obliquely ovate, auricled at the base; 

 trees. 

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

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

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



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

 tliick; 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. 

 Slirubs or small shrub-hke trees; bark sliining, dark red-brown, smooth; 

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

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

 rounded at the base; twigs densely glandular-resiniferous. 



7. B. fonlinalis. 



