21. =Pìnus Banksiàna=, Lambert. (GRAY OR NORTHERN SCRUB PINE.) Leaves in twos, short, 1 in. long, oblique, divergent from a close sheath. Cones lateral, conical, oblong, usually curved, 1½ to 2 in. long, the scales thickened at the end and without points. A straggling shrub, sometimes a low tree, found wild in the extreme Northern States. [Illustration: P. édulis.] [Illustration: P. monophýlla.] 22. =Pìnus édulis=, Engelm. (PIÑON OR NUT-PINE.) Leaves mostly in pairs, rarely in threes, 1 to 1½ in. long, from short sheaths, light-colored, rigid, curved or straightish, spreading; cones sessile, globose or nearly so, 2 in. long; tips of scales thick, conical-truncate, no awns or prickles; seeds large, nut-like, wingless, edible. A low, round-topped tree, branching from near the base, 10 to 25 ft. high; from the Rocky Mountains. A fine small pine; cultivated in the East. It needs some protection at Boston. The figure shows the seed. =Pìnus monophýlla=, Torr. and Frem., from the mountain regions farther west, has its leaves in ones and twos; when in ones, round and very rigid; when in pairs, flat on the inner side; leaves on the young shoots bluish, glaucous green, or silvery. This is probably only a variety of P. edulis. The seeds of both are so large and nutritious that they are extensively used for food by the Indians. GENUS =94. PÌCEA.= (THE SPRUCES.) Leaves evergreen, scattered (pointing in every direction), needle-shaped, keeled above and below, thus making them somewhat 4-sided. Fertile catkins and cones terminal; cones maturing the first year, pendulous; scales thin, without prickles, persistent, the cone coming off the tree whole. * Leaves very short, usually ¼ to ½ in. long, obtuse 7, 8. * Leaves usually ½ in. or more long, acute. (=A.=) =A.= Cones over 3 in. long; cultivated. (=B.=) =B.= Leaves dark green; large tree, common 3. =B.= Leaves bright or pale green 4, 5, 6. =A.= Cones 2 in. or less long; large native trees 1, 2. [Illustration: P. nìgra.] 1. =Pìcea nìgra=, Link. (BLACK OR DOUBLE SPRUCE.) Leaves about ½ in. long, erect, stiff, somewhat 4-sided, very dark green or whitish-gray; branchlets pubescent. Cones persistent, 1 to 1½ in. long, ovate or ovate-oblong, changing from dark purple to dull reddish-brown; scales very thin, roundish, with toothed or uneven edges. A conical-shaped tree, 40 to 80 ft. high; wild in the North and along the Alleghanies; often cultivated. Bark dark brown; branches horizontal; wood light reddish. Var. _rubra_ has larger, darker leaves, and larger, brighter-colored cones. [Illustration: P. álba.]