KEY, BASED UPON LEAVES. 9 



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



41. OSTRYA VlRGINICA. 



Unequally and sharply serrate, nutlet subtended by a leafy 



bract 42. CARPINUS CAROLINIANA. 



h?. 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. 



t f. Thickish and bark white 4o. BETULA PAPYRACEA. 



gr 2 . Veins incurved. 



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



Acuminate 65. MORUS RUBRA. 



Obtuse or rounded at apex 97. POPULUS IIETEROPHYLLA. 



7fc 2 . Orbicular-ovate ; petioles laterally compressed. 



Coarsely dentate 18. POPULUS GRAND IDENTATA. 



Serrate-dentate 72. Poi JLUS TREMULOIDES. 



/ 3 . 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. 

 h 2 . Serrate with teeth sharply 



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



Mucron ate arid 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 under surface. .56. PRUNIS AVIUM. 

 gr 6 . Ovate ; petioles short, generally not more than | in. 



168. ALNUS RHOMBIFOLIA. 



Long very smooth and shining above 57. PYRUS COMMUNIS. 



gr 1 . Wedge-obovate, veins very prominent, 



Thin, smoothish and dull above 58. CRATAEGUS PUNCTATA. 



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

 gr 8 . Ovate-oblong, veins incurved and petioles 



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



h*. Without glands, 



Glabrous both sides, sharply serrate. 



59. AMELANCHIER CANADENSIS. 



Downy under-side and petiole 30. PYRUS MALUS. 



gr 8 . Lanceolate oblong, 1-3 in. long, about equally acuminate at both 



ends 111. FORESTINA ACUMINATA. 



/*, Equilateral and truncate at base, 



gr. Serrate-dentate with cartilaginous teeth 



Deltoid ovate 48. POPULUS MONILIFERA. 



Broadly deltoid 73. POPULUS DILATATA. 



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

 \ Pinnately lobed ; lobes 



f. Rounded at apex (not bristle-pointed) and 

 gr. Subequal sinuses 



Wide, lobes narrow and nearly entire ; leaves 5-9 in. long. 



38. QUERCUS ALBA. 

 Narrow, lobes wide and 

 mostly undulate or crenate-toothed ; leaves 2-3 in long. 



160. Q LOBATA. 

 Entire or nearly so and round or obtuse at apex. 



136. Q. GARRY ANA. 



