WINTER KEY TO THE SPECIES OF POPULUS
| a. | Branches erect, more or less appressed to the main stem,forming a narrow, spire-like crown. | P. nigra italica, p. [59]. | |||
| aa. | Branches spreading, forming a broad crown. | ||||
| b. | Terminal buds 1/8-1/4 inch long, not resinous. | ||||
| c. | Buds and twigs more or less conspicuously white-downy;twigs green. | P. alba, p. [47]. | |||
| cc. | Buds and twigs not conspicuously white-downy; twigsusually red-brown. | ||||
| d. | Terminal buds about 1/8 inch long, puberulous, dusty-looking;lateral buds widely divergent; twigs rathercoarse. | P. grandidentata, p. [51]. | |||
| dd. | Terminal buds about 1/4 inch long, glabrous, lustrous;lateral buds more or less appressed; twigs ratherslender. | P. tremuloides, p. [49]. | |||
| bb. | Terminal buds 1/2-1 inch long, sticky-resinous. | ||||
| c. | Terminal buds about 1/2 inch long; buds not fragrant;twigs usually yellow, more or less strongly angled. | P. deltoides, p. [57]. | |||
| cc. | Terminal buds nearly 1 inch long; buds fragrant; twigsusually red-brown and seldom strongly angled. | P. balsamifera[E] p. [55]. P. candicans[E] p. [55]. | |||
White Poplar
1. Winter twig, × 1.
2. Portion of twig, enlarged.
3. Leaf, × 2.