Stem slender, 8—12 inches high, from a narrow fusiform tuberous root. Leaves linear, acute, 2—4 inches long, about ½ an inch wide. Spike of flowers slender, lax; bracts, lanceolate, acuminate, the lower slightly longer than the flowers; flowers pure white with a spicy fragrance; upper sepal ovate-lanceolate, obtuse, the lateral ones linear-lanceolate, acute, and strongly veined; petals narrowly linear-lanceolate equalling the sepals; lip lanceolate with an ovate rhomboid base about ¼ of an inch long; spur slender and curved, slightly exceeding the lip. In more or less shaded bogs through the Rockies, flowering during July. [Sidenote: =Ibidium romanzoffianum= (Cham.) House. _Lady’s Tresses._] Stem smooth, 6—18 inches high, leafy below, bracted above; the lower leaves 3—8 inches long, linear or linear-oblanceolate. Head of flowers more or less glandular, hairy, 2—4 inches long, half an inch or more thick, bracts shorter than the flowers; flowers waxy white or greenish, nearly half an inch long with an open mouth, spreading horizontally and very fragrant; upper sepals broad and obtuse; lip oblong, broad at the base, and contracted below to the crisped apex, thin, transparent, and veined, callosities merely thickenings of the basal margins of the lip. Throughout the region in springy places and wet alpine meadows; flowering toward the end of July. SALICACEÆ _Willow Family_ Trees or shrubs with light wood, brittle twigs, and simple alternate leaves; flowers borne in catkins; the staminate and pistillate on separate plants, the seed provided with a covering of long, white, silky, hairs. [Sidenote: =Populus balsamifera= L. _Balsam Poplar._] A large tree with nearly smooth gray bark, reaching a maximum height of 80 feet; branches stout, ascending, the larger buds very resinous. Leaves smooth, broadly ovate or ovate-lanceolate, entire, dark green and shining above, pale beneath, acute or acuminate at the apex, rounded or acute at the base, petioles round. Flowers in slender catkins, the staminate and pistillate on separate trees. Throughout the region in the river valleys and on the surrounding slopes, usually a tree not over 20—30 feet high but sometimes attaining an immense size. [Sidenote: =Populus tremuloides= Michx. _American Aspen._] A slender tree with smooth, light green bark, seldom more than 40—50 feet high, and less than half that in our region. Leaves smooth when young except on the margins, ovate, short-acuminate at the apex, rounded at the base, finely crenulate all around; petioles flattened laterally, very slender, causing the leaves to quiver with the slightest breeze. Flowers in rather stout catkins. Frequent in the low valleys and slopes through the Rockies, forming groves, or singly.