60 The New York State College of Forestry 



LEAF KEY TO THE SPECIES — (Continued) page 



121. Petioles about ^ of an inch in length Ostrya virginiana 157 



121. Petioles about § of an inch in length Carpinus caroliniana 159 



122. Leaves ovate to elliptical, oval or obovate; leaf base rounded or some- 

 what cordate 123 



122. Leaves rhombic-ovate; leaf-base cuneate or subtruncate. . Betula nigra IQ') 

 123. Leaves ovate-oval to oblong or obovate, 1 3/5-4 inches long; margin 



obscurelj^ doubly serrate Amelanchier canadensis 241 



123. Leaves ovate to oblong-ovate or elliptical, 2^-6 inches long; margin 



obviously double serrate 124 



124. Leaves bright green above, thickish; base generally heart-shaped. . . . 



Betula lenta 161 

 124. Leaves dull green above, membranous; 1 ase rounded or somewhat 



heart-shaped Betula lutea 163 



125. Leaves triangular to rhombic-ovate, very taper-pointed; petioles slender, 



|-1 inch long Betula populifolia 167 



Betula nigra 165 

 125. Leaves ovate, somewhat taper-pointed; petioles stout, ^-5 of an inch long. . 



Betula alba, var. papyrifera 169 

 126. Lateral veins prominently arcuate, extending from near the base nearly 



to the apex Rhamnus cathartica 305 



126. Lateral veins not prominently arcuate 127 



127. Leaves round-ovate to orbicular 128 



127. Leaves ovate-lanceolate to oval, oblong, or obovate 129 



128. Foliage fragrant, somewhat glaucous; petioles terete. .Prunus Mahaleb 253 

 128. Foliage neither fragrant nor glaucous; petioles conspicuously flattened . . 



Populus tremuloides 129 



129. Petioles glandular at the top, generally with cherry taste 130 



129. Petioles eglandular, without cherry taste 134 



130. Leaves smooth above, glabrous or sparingly pubescent on the veins 



below 131 



130. Leaves somewhat rugose above, pubescent below Prunus nigra 259 



Prunus domestica 263 



131. Leaf-margin regularly serrate 132 



131. Leaf-margin irregularly serrate or crenate-serrate 133 



132. Leaves oblong-lanceolate to oval, or lance-obovate; serrations blunt, 



incurved, glandular Prunus s rotina 245 



Prunus pennsy^vanica 249 

 132. Leaves ovate to elliptical or obovate; serrations attenuate, asclending, 



eglandular Prunus virginiana 247 



133. Leaves ovate, oblong, oval, or obovate, thin and rather flaccid 



Prunus avium 255 

 Prunus nigra 259 



133. Leaves ovate lanceolate to narrowly obovate, thick and firm 



Prunus Cerasus 257 



134. Leaves pubescent beneath 135 



134. Leaves glabrous beneath aside from the veins or veins axils 137 



135. Leaves close white-woolly pubescent beneath; petioles f-2 inches in length. . 



Pyrus Malus 235 

 135. Leaves pale greenish or grayish pubescent beneath; petioles ^-1 inch long 136 



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



136. Leaves glabrous and somewhat rugose above Prunus nigra 259 



Prunus domestica 263 



137. Leaves white glaucous beneath Salix discolor 121 



137. Leaves pale green beneath 138 



138. Leaves thin, with tufts of hairs in the vein axils on the lower side; 



petioles about \ inch in length Fagus grandifolia 171 



138. Leaves thick, without axillary tufts of hairs; petioles ^-1 inch in 



length Amelanchier canadensis 24 1 



139. Petioles conspicuously flattened 140 



139 Petioles terete or nearly so 142 



140. Leaves deltoid or deltoid-ovate Populus deltoides 139 



140. Leaves ovate to orbicular 141 



