

ANALYTICAL KEY TO THE GENERA XX1U 



Leaves pubescent on both sides, rugulose above; petioles l'-2' 

 long, like the young branchlet densely pubescent. 



Leitneria (p. 167). 



Leaves glabrous and smooth above, glabrous or pubescent be- 

 low ; petioles and branchlets usually glabrous or nearly so at 

 maturity. Nyssa (p. 779). 



Branchlets without a terminal bud. 



Pubescence consisting of simple hairs or wanting. 



Leaves 4'-6' long, pubescent beneath while young; branchlet 

 light brown or gray. Diospyros virginiana (p. 821) . 



Leaves 1^' 3' long, glabrous; branches light yellowish gray. 



Schoepfia (p. 336) 



Pubescence stellate; leaves obovate or elliptic, 2'-5' long, pu- 

 bescent below. Styrax (p. 829). 

 dd Leaves obtuse or acute. 



Branchlets not spinescent. 



Leaves glabrous at maturity, their petioles slender. Cotinus (p. 657). 

 Leaves pubescent below at maturity; their petioles short and thick. 



Diospyros texana (p. 823). 

 Branchlets spinescent; leaves often fascicled on lateral branchlets. 



Bumelia (p. 812). 

 aa Leaves serrate or piunately lobed. 



b Stipules present, (bb, see p. xxvi.) 

 c Winter-buds naked. 



Leaves oblique at base, the upper side rounded or subcordate, obovate, 

 coarsely toothed. Hamamelis (p. 368). 



Leaves equal at base, cuneate, finely serrate or crenate. 



Rhamnus sp. 2, 3 (p. 724, 725). 

 cc Winter-buds with a single pair of connate scales. 



Primary veins arching and uniting within the margins; leaves simply serrate 



or crenate, sometimes entire. Salix (p. 138). 



Primary veins extending to the teeth, leaves doubly serrate, often slightly 



lobed. Alnus (p. 220). 



ccc Winter-buds with several pairs of imbricate scales. 



d Terminal buds wanting; branchlets prolonged by an upper axillary bud. 

 Juice milky; leaves usually ovate, often lobed. Moms (p. 328). 



Juice watery; leaves not lobed. 

 Leaves distinctly oblique at base. 



Leaves with numerous prominent lateral veins. 



Leaves generally broad-ovate, simply serrate, stellate-pubescent 



at least while young, rarely glabrous. Tilia (p. 732). 



Leaves never broad-ovate, usually doubly serrate, more or less 



pubescent with simple hairs, at least while young. 

 Winter-buds ovoid, usually acute, \ to nearly as long as peti- 

 oles; leaves l'-7' long, doubly serrate. Ulmus (p. 309). 

 Winter-buds subglobose, minute; leaves 2' 2^' long, crenate- 

 serrate. Planera (p. 316). 



Leaves 3 or 4-nerved from the base. C61tis (p. 318). 



Leaves slightly or not at all oblique at base. 



Leaves 3-nerved from the base, glandular-crenate or glandular- 

 serrate. Ceanothus (p. 726). 

 Leaves not or obscurely 3-nerved at base, usually doubly serrate. 

 Leaves blue-green; petioles \'-%' long; bark smooth, gray-brown. 



Carpinus (p. 201). 

 Leaves yellow-green. 



Bark rough, furrowed; petioles \'-\' long; leaves not resinous- 

 glandular. Ostrya (p. 202). 

 Bark flaky or cherry-tree like; petioles J'-l' long; leaves often 

 resinous-glandular while young. Betula (p. 205). 

 dd Terminal buds present. 



Primary veins arching and uniting within the margin (extending to the 

 margin in the lobed leaves of Mains). 



