Trees or shrubs with alternate simple leaves; staminate and pistillate flowers borne in separate catkins on the same plant; the staminate usually long, slender, and drooping; the pistillate short and erect; fruit cone-like.

Becoming a large forest tree; bark chalky white, peeling in thin layers. Leaves ovate, acute, or acuminate, dentate and denticulate, smooth above, glandular and hairy on the veins beneath, slender-petioled 1½—4 inches long. Staminate catkins 2—4 inches long; pistillate catkins ¾ of an inch or more long.

Sparingly on the slopes in the vicinity of Field, British Columbia; not a common tree.

A tree sometimes 100 feet high but much smaller in our region; the bark smooth dark bronze; twigs gray-brown, warty. Leaves broadly ovate or nearly orbicular, sharply serrate, short-petioled, smooth on both sides or sparingly hairy beneath ¾—2 inches long.

On river shores throughout the region, sparingly from Field west.

A shrub 1—8 feet with brown, glandular, warty twigs. Leaves orbicular, oval or ovate, smooth, rounded at the apex, crenate-dentate, bright green above, pale and sticky, glandular-dotted beneath, short petioled, ¼—1 inch long. Staminate catkins, commonly solitary, about ½ an inch long; cones when ripe ½—1 inch long.

In moist ground and thickets in the lower valleys through the Rockies, frequent.

A shrub 4—20 feet high with brown bark. Leaves more or less broadly ovate, 2—3 inches long, acute, rounded or slightly heart-shaped at the base, acutely doubly toothed, light green and smooth on both sides or slightly hairy. Staminate catkins slender, drooping, 1—2 inches long; fruiting cones erect, ½ an inch or less long.

In moist places and thickets and stream banks at the higher elevations throughout the region, very abundant in the Selkirks.