ll.\.M)i;(«)K i»K TkIvKS of TIIK Xl )K T 11 KK.N SrAli:s AM) ('a.xaha. 4i'7 



V Broad-ovato, cordate at liasc. imlc or rusty licneath P. candicaus. 



b* Ovati', jial(> or rusty liciicatli. roundel or widf cuni'alc- at liasr. liiirly ncnatc-scrrate, 



afuiiiiiuitc P. balsainifera. 



b" licart-sliapcd. lar^ic al.rupl at apex. cnMialc-sn rale and prti.drs sliulnly if ,m all 



tlattciuMl P, heterophylla. 



a' Buds not resin-coated: le.ives tjihicular-ovate ; petioles lonj; and 

 b Flattened laterally (.Ixpc/i.s ) and edses of leaves 



Finely crenate-serrate ; buds glabrous P. tremiiloides. 



Coarsely dentate ; buds scurfy-pubescent P. grandidentata. 



b' Slightly if at all flattened; leaves densely white-tomentose bi'ueatli. P. alba. 



For species see pp. 1)1-1 l-i nml the folloiriiii/: 



KiROi'EAN Bi-AC'K PoPLAK. /'. iilf/ra L. A large wide-spreading Kuroiiean tree and nearly 

 a century ago was reported (as /'. H udsoiiicii Michx. and /'. iKtiilifolid I'ursh.) as naturalized 

 in this country, but it is rare in a naturalized state. The characters given below are of the 

 typical J'. ni(ir(i. and are equally applicable to the Loinbardy I'oi)lar (var. linlicd) exce|)t as 

 noted in the consideration of that tree. Lcarcs broad-deltoid, wide-cuneate or almost truncate 

 at base, abruptly acuminate at apex, crenate. pubescent at first but finally glabrous, firm, the 

 blade usually wider than long; i)etioles long, slender and laterally comiu-essed. Floinrs: 

 staminate anients l%-3 in. becoming longer; stamens about 20; pistillate auients 2-lj in. long, 

 becoming longer. fniif: capsules oblong, obtuse, short-stalked. 



BIRCH FAMILY. BETULACE^. 



Trees and a few shrubs of the northern hemisphere commonly with fragrant aromatic 



properties and grouped in six genera of which five are found in North .Vmerica. They have 



the following characters in common : 



Leaves simple, alternate, petioled, pinniveined. obliquely pli<'ate in venation, deciduous; 

 stipules fugacious; branchlets terete. Floinrs in early spring before or with the unfolding of 

 the leaves, monoecious; the staminate in elongated pendulous lateral aments, in the axils 

 of the bracts of which are borne 1-8 stnall flowers, with or without calyx and 'J-20 small 

 erect stamens inseited on the receptacle, with distinct filaments and 2-celled extrorse anthers 

 opening longitudinally ; pistillate flowers in short spike-like or capitate aments, from lateral buds 

 with or without calyx, with 2-celled ovary and 2-cleft or bifurcate style stigmatie at the apex 

 or on the inner surfaces of tb.e branches and a single anatropous pendulous ovule in each 

 cell of the ovary. Fruit a small mostly 1-celled l-seeded nut or samara; seed solitary, 

 suspended, without allnimen, with large and fleshy cotyledons and short radicle. 



KEY TO THE GENERA. 



a Nutlet wingless, from the axils of deciduous scales and more or less inclosed in an 

 invoiucie ; staminate flowers solitary in the axils of the scales of the ament and without 

 calyx ; involucre of fruit 

 b Hat, open, 3-cleft and foliaceous ; staminate aments in winter inclosed with bud-scales. 



Carpinus. 



b' A closed bladder-like sac ; staminate aments in winter naked Ostrya. 



a' Nutlet more or less winged, in the axils of ])ersistent scales and without involucre; 

 staminate flowers .S-(> together in the axils of the scales of the aments and with calyx; 

 bracts of the fruiting aments 

 b Three-lobed, thin and deciduous; stamens 2 with 2-branched filaments; winter i)ud3 



covered with scales Betiila. 



b^ Erose or .")-lobed. thickened, wood.\- and persistent; wings of nutlet more or less reduced; 

 winter buds naked Alnus. 



THE HORNBEAMS. Ge.nus CARPI XUS L. 



Trees of about a dozen species with smooth gray Beech-like bark, furrowed and ridged 

 trunks, and confined to the northern hemisphere, but only one is found native in North 

 America. The following are the generic characters: 



Leaves ovate, acjite or acuminate, with nearly straight prominent veins. Flowers in 

 April; staminate anients i)endulous and with lUduiineni nearly sessile broad ovate acute 

 scales, in the axils of which are found the naked flowers consisting of several stamens with 

 short slender two-branched filaments, each branch bearing a 1-celled half-anther hairy at 

 apex; pistill.-ite aments slender, few-flowered and terminal on leafy branchlets of the year, 

 with small deciduous scales, each subtended by a pair of flowers wliich are furnished each 

 with a small acute bract and pair of bractlets; calyx adnale to the ovary: stigmas 2. subulate. 

 Fruit a small comjji'essed ovoid i)rominentlv ribbed nut. tipped with calvx-lobes and attached 

 at its base until maturity to :i large foliaceous .•'.-lobed jiale-green involucr.- formed from the 

 enlarged bract and bract l.'ts of the flower. 



Carpi)iiis is the ancient Latin name of the Euroiiean llnrnfuain. 



For xjXiicn see jtp. tl'i-lt't. 



