CUPULIFEILE-URTIC.'ACEJE 301 



a. Brown-barked birches: leaves ovate. 



B. 16nta, Linn. Cherry birch. Sweet birch. Tall tree, the l>ark tight 

 (not peeling in layers), the twigs very aromatic: leaves oblong-ovate, Bome- 

 whai cordate at base, doubly serrate, becoming flossy above: bracts of the 

 oblong-cylindric fruiting catkins with wide-spreading lobes. Rich woods. 



B. lutea, Siichx. Fellow <<r gray birch. Bark grayer or silvery, peel- 

 ing in layers: leaves scarcely cordate, dull, more downy: liracts of the 

 short-oblong fruiting catkins with scarcely spreading scales: tree less aro- 

 matic than the other. Same range. 



aa. White-barked birches: leaves triangular ; broad-ovate. 



B. papyrifera, Marsh. /''/"/ birch. Canoi birch. Tree of medium 

 to rather large si/..-, with tin- hark peeling in very large plates or layi rs 

 leave- broad-ovate and often somewhat cordate, dull green. Penn., north. 



B. populifolia, Ait. American whitt birch. Small and --lender tree with 

 rather tight, glistening, white- bark: leaves triangular-acuminate, toothed, 

 dangling, and moving incessantly in the- wind. Northeastern states. 



B. alba, Linn. European whiU birch. A larger tree, with triangular 

 ovate leaves which are pointed hut not lonir-acuminate. Kurojie; the com 

 mon cultivated white bireh. 



4. ALNUS. Aldkb. 



.Much like Betula, hut -malh-r tree- or bushes: Bowers with ;t 



parted calyx, and the small, short, fertile catkins composed of thickened. 

 woody scales. In the following, tin- Bowers appear before tin- leaves in 

 earliest spring, from catkins formed the previous year and remaining partly 

 developed during winter. Common along streams. 



A. incana, W'illd. Speckled alder. Shrub or small tree, with pubescent 

 branches: leaves oval to oblong-ovate, acute, doubly serrate, glaucous and 

 downy underneath: es about ' , in. long, stly Bessile. 



A. rugosa, S|u-eiiL r . [A. serrulata, W'illd. i. 8mooth alder. Leaves 

 elliptic or obovate, acute or rounded al the apex, Bnely Berrate, the under side 

 of the leaves -t th or pubescenl only on the veins: cones short stalked. 



A. glutinbsa, Gertn. Black alder. Leaves orbicular or verj broadly 



obovate, not acute, Irregularly Berrate, dull .-end nearly si th beneath: 



cones peduncled. Europe; planted, some varieties with divided leaves. 



yiii. rkTK'Ai'K.i:. Nettle Family. 



Trees and herbs, with small apetaloue flowers in small clusters or 

 solitary : leave- mostly Btraight-veined, with stipules: plants dicBcious 

 or monoecious, or flowers perfect in the elms: Btamens usually as many 

 :i- the lobes of the calyx and o|i|(usite them: ovary Buperior, ripening 

 into a l seeded Indehiscent, often winged fruit. A.verj polymorphous 



ciation, bj Borne botanists divided Into two or three ordinate 



