The Trees of Vermont 61 



WINTER KEY TO THE SPECIES OF POPULUS 



a. Branches erect, more or less apprcssed to the main stem, forming 



a narrow, spire-Hke crown P. nigra italica, p. 75. 



aa. Branches spreading, forming a broad crown. 

 b. Terminal buds ys-yi inch long, not resinous. 



c. Buds and twigs more or less conspicuously white-downy ; twigs 



green P. alba, p. 63. 



cc. Buds and twigs not conspicuously white-downy ; twigs usually 

 red-brown. 



d. Terminal buds about Ys. inch * long, puberulous, dusty- 

 looking ; lateral buds widely divergent ; twigs rather 



coarse P. grandidentata, p. 67. 



dd. Terminal buds about J4 i^^^'l^ lo"g» glabrous, lustrous ; lateral 

 buds more or less appressed ; twigs rather slender, 



P. tremuloides, p. 65. 

 bb. Terminal buds y^-l inch long, sticky-resinous. 



c. Terminal buds about ^ inch long ; buds not fragrant ; twigs 

 usually yellow, more or less strongly angled, 



P. deltoides, p. 73. 

 cc. Terminal buds nearly 1 inch long ; buds fragrant ; twigs usually 

 red-brown and seldom strongly angled, 



P. balsamifera,^ p. 69. 

 P. candicans/ p. 71. 



1 It is difficult to distinguish between tfiese species in tlie absence of summer 

 cliaracters. If leaves can be found on or beneath a tree which is sufficiently segre- 

 gated from similar trees as to avoid any chance for error, the summer key on the 

 opposite page may be used. 



