56 The Neiv York State College of Forestry 



LEAF KEY TO THE SPECIES — (Continued) page 



27. Leaves broadly ovate to oval; lateral veins prominently arcuate 



Rhamnus cathartica 305 

 27. Leaves ovate toelli ptical, oval or obovate; lateral veins not prominently 



arcuate 28 



28. Leaves abruptly acuminate at the apex Viburnum Lentago 341 



28. Leaves rounded or acute at the apex Viburnum prunifolium 343 



29. Leaves 3-lobed near the apex ; lobes finely doubly serrate 



Acer pennsylvanicum 239 



29. Leaves 3-7 lobed ; lobes not finely serrate 30 



30. Leaves glabrous or nearly so beneath 31 



30. Leaves pubescent beneath 33 



3L Leaves pale green beneath; leaf-lobes sinuately toothed Acer saccharum 293 



31. Leaves greenish white or silvery white beneath; leaf -lobes coarsely dentate or 



serrate 32 



32. Sides of terminal lobe converging Acer rubrum 299 



32. Sides of terminal lobe diverging Acer saccharinum 297 



33. Leaves membranous; leaf-lobes coarsely crenate-serrate A.cer spicatum 291 



33. Leaves rather thick; leaf-lobes entire or somewhat undulate 



Acer saccharum, var. nigrum 295 



34. Leaves palmately compound ; leaflets 5-7 Aesculus Hippocastanum 303 



34. Leaves pinnately compound or in part decompound 35 



35. Leaflets 3-5 (rarely 7 or 9) , coarsely and irregularly serrate above the middle, 



lobed or divided Acer Negundo 301 



35. Leaflets 5-11, obscurely or sharply serrate, with fine remote teeth 36 



36. Leaflets sessile on the rachis Fraxinus nigra 333 



36. Leaflets stalked 37 



37. Leaf-rachis pubescent Fraxinus pennsylvanica 329 



37. Leaf-rachis glabrous 38 



38. Leaflets obscurely crenulate-serrate, pale white beneath 



Fraxinus americana 327 



38. Leaflets sharply serrate, light green beneath 



Fraxinus pennsylvanica, var. lanceolata 331 



39. Leaves simple 40 



39. Leaves compound 151 



40. Leaf-margin entire 41 



40. Leaf-margin not entire 56 



41. Leaves prevailingly linear-lanceolate or lanceolate to narrowly elliptic, 



spatulate, or narrowly obovate 42 



41. Leaves prevailingly ovate, oval-elliptical or obovate 46 



42. Leaves minutely downy and rugose-veined above Salix rostrata 123 



42. Leaves smooth or nearly so above, not rugose-veined 43 



43. Leaves subopposite, oblanceolate to spatulate Salix purpurea 125 



43. Leaves distinctly alternate 44 



44. Leaves oblong-lanceolate to narrowly elliptic or obovate, white glaucous 



beneath 45 



44. Leaves linear-lanceolate to oblong, pale green beneath . . Quercus phellos 199 



45. Leaves conspicuously reticulate- venulose; secondary veins arcuate 



Salix discolor 121 

 45. Leaves not conspicuously reticulate- venulose; secondary veins not arcuate. . 



Magnoha virginiana 217 

 46. Leaves broadly ovate to reniform, palmately 5-7 nerved; petioles 



thickened at the top Cercis canadensis 271 



46. Leaves ovate to elliptical, oval, or obovate, with primary midrib and 



secondary veins; petioles not thickened at the top 47 



47. Petioles exuding a milky juice when broken Madura pomifera 209 



47. Petioles not exuding a milky juice when broken 48 



48. Petioles j-f of an inch long 49 



48. Petioles 1-4 inches long 52 



49. Leaves obovate to obovate-lanceolate, tapering at the base. . Asimina triloba 223 

 49. Leaves oblong to oval or broadly obovate, rounded or acute at the base. .50 



50. Leaves thin, pale green below, 4-10 inches long. . . .Magnolia acuminata 219 



50. Leaves thick, pale glaucous below, 3-6 inches long. . Magnoha virginiana 217 



51. Leaves lustrous green above, thick, 2-4 inches long Pyrus communis 231 



