A tree 20 or 30 feet high generally with a short trunk 2—4 feet in diameter, stout, very flexible branches, often standing nearly erect and forming an open irregular broad head; often a low shrub and nearly prostrate at high altitudes; bark thin with creamy-white plate-like scales; leaves stout, rigid, slightly incurved, clustered at the ends of the branches 1½—2½ inches long; cones oval or subglobose horizontal, sessile, dark purple, 1½—3 inches long with thickened acute scales. [Illustration: Pinus albicaulis Engelm. (¼ Nat.) White Pine.] [Illustration: Pinus Murrayana Oreg. Com. (¼ Nat.) Jack Pine.] On alpine slopes and exposed ridges from 5000 feet elevation upward, occurring occasionally in the Rockies, but frequent throughout the Selkirks at or near the timber line. [Sidenote: =Pinus Murrayana= Oreg. Com. _Black Pine, Jack Pine._] A tree 40—80 feet high with a trunk 1—3 feet in diameter, slender, strict; branches frequently persistent nearly to the base of the stem, somewhat pendulous below, ascending near the top of the tree, forming a pyramidal spire-topped head; bark thin, close, light orange-brown with appressed scales; leaves 2 in a bundle, yellowish-green, 1—3 inches long, stout; cones yellowish-brown and shining oval to sub-cylindric oblique at the base, often clustered ¾—2 inches long, with slightly concave scales with slender deciduous prickles. The most abundant tree at the lower altitudes throughout the Rockies, frequently covering vast tracts, and rising on the mountain sides to 6000 feet or occasionally higher. [Sidenote: =Larix Lyallii= Parl. _Lyall’s Larch._] A tree usually 40—50 feet high with a diameter of 18—20 inches and remote, elongated, tough, persistent, nearly black branches, with prominent winter buds with conspicuous long white matted hairs fringing the margins of their scales and often nearly concealing the buds; bark on the old trunks ½ to ¾ of an inch thick, pale gray, divided into shallow irregular plates; leaves many in a cluster, 4-angled, slender, blue-green 1—1½ inches long; young cones showy with dark red or yellow-green scales and dark purple bracts; when mature, ovate 1½—2 inches long with reddish-purple scales and long tipped dark purple bracts. [Illustration: Larix Lyallii Parl. (⅓ Nat.) Lyall’s Larch.] [Illustration: Thuja plicata Don. (⅓ Nat.) Giant Cedar.] An alpine tree occurring with more or less frequency throughout the Rockies from Banff to Field, from 6000 to 8000 feet elevation, at or near the tree limit, often much stunted and almost shrub-like; very abundant on the mountains in the region about Lake Louise. [Sidenote: =Abies lasiocarpa= (Hook) Nutt. _Sub-alpine Fir, Balsam Fir._]