KEY, BASED UPON LEAVES. 



i a . 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*. Thickish and bark white ........... 43. BETULA PAPYRACEA. 



gr 3 . Veins incurved. 

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



Acuminate ................................. 63. MOMS RUBRA. 



Obtuse or rounded at apex . ....... 97. POPULUS HETEROPHIFLA. 



/t 2 . Orbicular-ovate; petioles laterally compressed, 



Coarsely dentate ............... 18. POPULUS GRANDIDENTATA. 



Serrate-dentate .................. 72. POPULUS TREMULOIDES. 



3 . Equilateral and acute at base, tapering both ways. 



g. Linear-lanceolate, tomentose on midrib above and petiole. 



45. SALIX NIGRA. 

 gr 2 . Lanceolate or ovate-lanceolate, long-acuminate; capsules 



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



With slender pedicels. . ............... 71 . SALIX AMYGALOIDES. 



gr 3 . Oblong-lanceolate with teeth sharply 



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



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



Finely glandular-serrate ....... 55. PRUNUS PENNSYLVANICUM. 



gr 4 . Obovate-oblong, serrate, hairy under surface.. .56. PRUNUS AVIUM. 

 g 5 . Ovate, very smooth and shining ........... 57. PYRUS COMMUNIS. 



gr 6 . Wedge-obovate, veins very prominent. 



Thin, smoothish and dull above ...... 58. CRATAEGUS PUNCTATA. 



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

 gr 7 . 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. 



4 . Equilateral and truncate at base, 



g. Serrate-dentate with cartilaginous teeth 



Deltoid-ovate ................ . ....... 48. POPULUS MONILIFERA. 



Broadly deltoid ....................... .73. POPULUS DILATATA. 



Irregularly serrate or obscurely lobed ____ 70. BETULA POPULIFOLIA. 



innately lobed; lobes. 

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



g. Subequal ................................. 38. QUERCUS ALBA. 



gr 2 . Very unequal. 



h. The two lobes next the summit much the largest. 



92. QUERCUS OBTUSILOBA. 

 ft 2 . Lyrate-pinnatifid and sinuses extending 



Nearly to the midrib and roundish. .39. QUERCUS MACROCARPA. 

 Usually not over half-way to the midrid and more acute. 



66. Q. BICOLOR. 

 / 2 . Bristle-pointed; sinuses. 



g. Moderately deep and narrow, lobes broad ...... 15. QUERCUS RUBRA. 



gf 2 . Deeper and broader; lobes narrower .......... 93. Q. TINCTORIA. 



gr 3 . Deep, broad and rounded; lobes very narrow; acorn 

 Ovoid-oblong, immersed in coarse-scaled cup. 



69. QUERCUS COCCINEA. 

 Flatened -globular, 4 immersed in the fine-scaled cup. 



94. QUERCUS PALUSTRIS. 



2 . Broad, truncate at both base and apex, and with two spreading lobes on 

 each side .......................... 2. LIRIODENDRON TULIPIFERA. 



5 . Wavy and spinous-toothed, very thick ................ 52. ILEX OPACA. 



6 . Undulately crenate-toothed ; obovate to lanceolate. 



67. QUERCUS PRINUS. 



gr 2 . 



Pin 



