KEY, BASED UPON LEAVES. 

 Doubly and sharply serrate, nutlet inclosed in a papery sac. 



41. OSTRYA VIRGINICA. 



Unequally and sharply serrate, nutlet subtended by a leafy bract. 



42. CARPINUS CAROLINIANA. 

 W. Ovate and 

 i. Finely and closely serrate, smooth, whitish and reticulate-veined 



beneath 47. POPULUS BALSAMIFERA. 



i 2 . Doubly serrate and 

 J. Thinnish ; petioles downy and of aromatic flavor. 



Bark of trunk yellowish-gray 17. BETULA LUTEA. 



Bark reddish-brown 44. BETULA LENTA. 



j 2 . Thickish and bark white 43. BETULA PAPYRACEA. 



gr 2 . Veins incurved ; leaves 

 h. Orbicular-heart-shaped, thickish, 4-8 in. long. 



Acuminate 63. MORUS RUBRA. 



. Obtuse or rounded at apex 97. POPULUS HETEROPHYLLA . 



h*. Orbicular-ovate ; petioles laterally compressed ; leaves 



Coarsely dentate 18. POPULUS GRANDIDENTATA. 



Serrate-dentate 72. POPULUS TREMULOIDES. 



h 3 . Broad ovate, acuminate serrate 218. POPULUS TRICHOCARPA. 



h 4 . Elliptical to obovate, conspicuously netted-veined, above. 



Glabrous 207. PRUNUS SUBCORDATA. 



Hairy along veins 126. RHAMNUS PURSHIAXA. 



7i & . Ovate-lanceolate, pubescent beneath 209. PYRUS RIVULARIS. 



f z . Equilateral and acute at base, tapering both ways, 

 gr. Narrow-lanceolate, very long-attenuate, tomentose on midrib above 



and petiole 45. SALIX NIGRA. 



gr 2 . Ovate-lanceolate to lanceolate, long-acuminate, 2-4 in. long; capsules 



Sessile or nearly so 46. SALIX ALBA var. VITELLINA. 



With slender pedicels 71. SALIX AMYGDALOIDES. 



gr 3 . Oblong-lanceolate to lanceolate. 

 h. Minutely serrulate, 3-7 in. long ; petioles downy. 



140. SALIX LAEVIGATA. 

 ft 2 . Serrate with teeth sharply 



Awn-pointed and in about 20 pairs 40. CASTANEA VESCA. 



Mucronate and in 6-12 pairs 68. QUERCUS MUHLENBERGII. 



Finely glandular-serrate 55. PRUNUS PENNSYLVANIA. 



gr 4 . Oblanceolate to lanceolate-oblong, puberulous beneath. 



165. SALIX LASIOLEPIS. 

 gr 5 . Obovate-oblong, serrate, hairy beneath; length 



1-3 in., acute 208. PRUNUS MOLLIS. 



3-6 in., long acuminate 56. PRUNUS AVIUM. 



gr 6 . Ovate ; petioles. 



Short, generally not more than | in 163. ALNUS RHOMBIFOLIA. 



Long; leaves very smooth and shining above. .57. PYRUS COMMUNIS. 

 gr 7 . Wedge-obovate, veins very prominent, 



Thin, smoothish and dull above 58. CRATAEGUS PUNCTATA. 



Thick, smooth and lustrous above 85. CRATAEGUS CRUS GALLI. 



gf 8 . Ovate-oblong, veins incurved and petioles 



h. With 2-4 glands, smooth .'. . .29. PRUNUS SEROTINA. 



W. Without glands, 



Glabrous both sides, sharply serrate. 



59. AMELANCHIER CANADENSIS. 



Downy under-side and petiole ... .30. PYRUS MALUS. 



</ 8 . Lanceolate oblong, 1-3 in. long, about equally acuminate at both ends. 



111. FORESTIERA ACUMINATA. 



f 4 . Equilateral and truncate at base, 

 (/. Serrate-dentate with cartilaginous teeth 



Deltoid -ovate, rather long taper-pointed 48. POPULUS MONILIFERA. 



Deltoid-reniform, more abruptly pointed. . .194. POPULUS FREMONTII. 



Broadly deltoid 73. POPULUS DILATATA. 



gr 2 . Irregularly serrate or obscurely lobed 70. BETULA POPULIFOLIA. 



e 3 . Pinnate! y lobed ; lobes at apex 

 f. Rounded (not bristle-pointed) and 



