Sepals united; petals long clawed. Calyx 10-many nerved. Styles 3; capsule with 3 or 6 teeth. =Silene.= Styles 5; capsule with 5 or 10 teeth. =Lychnis.= Sepals free to the base or nearly so. Petals two-cleft or rarely none. Capsule cylindric, usually curved. =Cerastium.= Capsule ovate or oblong, not curved. =Alsine.= Petals entire or notched, rarely none. Styles as many as the sepals and alternate with them. =Sagina.= Styles fewer than the sepals. Seeds appendaged. =Mœhringia.= Seeds not appendaged. =Arenaria.= [Illustration: Silene acaulis L. (⅔ Nat.) Moss Campion.] [Illustration: Lychnis apetala L. (⅔ Nat.) Nodding Lychnis.] [Sidenote: =Silene acaulis= L. _Moss Campion._] Closely tufted, an inch or two high, forming cushion-like beds, often 2 feet or more across. Leaves sessile, crowded, linear, ½ an inch or less long, the margins ciliate. Flowers ¼ of an inch or more across, nearly sessile or raised on naked curved peduncles, often ½ an inch long; calyx narrowly campanulate, ¼ of an inch long, smooth, the teeth short, rounded; petals rose-purple or rarely white, entire or notched. In alpine meadows, in stony ground, on the moraines and tops of the mountains throughout the region, flowering in June and July. [Sidenote: =Silene Lyallii= S. Wats. _Lyall’s Catchfly._] Stems slender, decumbent at the base, 12—18 inches high, minutely hairy throughout, glandular above. Leaves, the basal spatulate, obtuse 1—2 inches long on long petioles, those of the stem linear 1—2 inches long, sessile. Flowers on short peduncles in rather loose terminal heads; calyx oblong, inflated, about ½ an inch long, narrow, glandular, teeth purple-tipped; petals white, nearly half an inch long, spreading, two-lobed. On grassy alpine slopes throughout the region, flowering in June and July. [Sidenote: =Lychnis apetala= L. _Nodding Lychnis._] More or less glandular-hairy, 2—6 inches high. Leaves linear or oblanceolate, ½-2½ inches long. Flower solitary, ½—¾ of an inch long, nodding; calyx inflated, strongly purple veined, its teeth triangular-ovate, acute; petals purple, as long as or shorter than the calyx, narrow, 2-cleft. Among loose boulders on the moraines and alpine summits throughout the region, flowering in July. [Sidenote: =Cerastium arvense strictum= (L.) Rydb. _Field Chickweed._] Stems tufted, ascending from a decumbent base, 3—6 inches high, hairy throughout, roughly so at the base; glandular at the summit. Leaves numerous, ½—¾ of an inch long, narrowly lanceolate, acute, with a broad sessile base. Flowers several in a more or less close head, nearly half an inch broad, white; petals deeply notched. In dry stony ground in the lower valleys of the Rockies, flowering in June.