95 



SUMMER KEY TO THE SPECIES. 

 1. Leaves with round or channeled petioles; twigs with orange colored pith, ^*^°' 



1. Leaves with flattened petioles; twigs with white pith .^! . .'!°*!°'.^^."2 '^ 



2. Leaves broadly deltoid, abruptly acuminate; stigma-lobes expanded in all direc- 



tlons _ J 1* -J 



2. Leav^es broadly ovate to nearly roun(i;'nsualVy'acuVe "at ■apeiV'stigma-lobes \h°M- ^' 



3 



3. Leaves finely serrate on margin; bark greenish-white P. tremuloides 96 



3. Leaves coarsely dentate on margin; bark yellowish-gray to black, P. g-randidentata 97 



WINTER KEY TO THE SPECIES. 



1. Terminal buds } to 3 of an Inch long, decidedly resinous; lateral branches with a tend- 

 ency 10 bi'cnme vertical p ^eltoidcs 



1. Terminal buds about 1 of an inch long, devoid of rcsinor'onVy'slVehtiy' resinous; lateral 



branches without the vertical tendency .... "'>.'"^ 



2. Twigs with orange-colored pith ' p i,„,„„„i,„ii. „„ 



Twigs with white Dith. ..... ^' >'«'"''l"'ylla 98 



.3 



2. Twigs with white pith, 



3. Buds smooth, glossy, conical, sharp-polnted ; often incurved and closely appressed 



bari! greeniirh-white t. * . -j 



o r,„ 1 1 ■ ,, ^' tremuloides 96 



3. Buds downy, dull, ovate, blunt-pointed, straight, divergent; bark ycllowlsbgrnv 



to black — jj . ,' 



P. grandidentata 97 



