KEY, BASED UPON LEAVES. 5 



i 2 . Doubly serrate and 



J. Tkinish; 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. 



h 3 . Orbicular-ovate with large irregular teeth and long petiole. 



18. POPULUS GRANDIDENTATA. 



gr 2 . Veins incurved, leaves thickish, 



Smooth, petioles with 2-4 glands 29. PRUNUS SEROTINA. 



Downy on under surface and petioles .30. PYRUS MALUS. 



/" 2 . Equilateral and acute at base, tapering both ways. 



Linear-lanceolate, toinentose on midrib above and petiole. 



45. SALIX NIGRA. 

 Lanceolate or elliptic-lanceolate, smooth above. 



46. SALIX ALBA, var. VITELLINA. 

 Oblong-lanceolate with mucronate teeth, one at the end of each 



vein 40. CASTANEA VESCA, var. AMERICANA. 



f s . Equilateral and truncate at base, deltoid or deltoid-ovate, serrate- 

 dentate 48. POPULUS MONOLIFERA. 



e 3 . Pinnatifid or lobed. 

 f. Moderately pinnatifid. 



g. Oval, lobes bristle-pointed 15. QUERCUS RUBRA. 



Lobes obtuse and rounded 38. QUERCUS ALBA. 



0r 2 . Obovate or oblong and lyrate-pinnatifid. 



39. QUERCUS MACROCARPA. 

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



on each side 2. LIRIODENDRON TULIPIFERA. 



ei 2 . Main ribs several palmately- veined, etc. 

 . Rib single at first but soon sending off a strong vein on each side and 



leaves 3-lobed, 2-lobed or entire 32. SASSAFRAS OFFICINALE. 



e 2 . Ribs three at first, but soon five by branching, leaves alternate, base of 

 petiole concave and fitting over the axillary bud. 



13. PLATANUS OCCIDENTALIS. 



e z . Ribs 5-7 from commencement; leaves opposite, base of petiole subtend- 

 ing (not covering) the axillary bud. 



Moderately incised with broad divisions and rounded sinuses. 



7. ACER SACCHARINUM. 

 Deeply incised with narrow divisions and acutish sinuses. 



26. ACER DASYCARPUM. 



c 2 . Needle-shaped without distinction of blade and petiole short, about 1 

 in. in length, soft and in fascicles of many each... 23. LARIX AMERICANA. 

 ft 2 . Compound Leaves. 



c. Palmate, with 7 obovate, serrate leaflets 6. AESCULUS HIPPOCASTANUM. 



c 2 . Pinnate and with an odd terminal leaflet. 

 d. Leaflets all petiolulate. 



e. Leaflets numerous, 21-41 each with one or two pairs of glandular teeth 

 at its base.. . . .4. AILANTHUS GLANDULOSUS. 



