CERA'STIUM (from tapas, a horn), a genus of plants belonging to the natural order Caryophyllacem It has a 5-parted calyx, 5 petals, all bifid; stamens 1,0, 5, or 4 ; styles 5 or 4 ; the capsules tubular, opening at the end, with 10 teeth. This is an extensive genus, con taining species which are common weeds in the temperate climates of moat parts of the world. Don enumerates 82 species; of these 9 are British.
C. alpinum, Alpine Mouse-Ear Chickweed, has a hairy ascending stem, the leaves ovate, ovate-oblong, or lanceolate; the flowers few ; the sepals bluntish, with membranous margins; bracts herbaceous, their margins often narrowly membranous ; the capsules, at length, twice as long as the calyx. This plant is a native of the Pyrenees, the mountainous parts of Wales and Scotland, and of Melville Island. It is subject to great variations, and a number of varieties have been described by Brown, Bentham, and other botanists.
C. glomeratum has ovate leaves, acute lanceolate scpala, with a narrow membranous margin, and, as well as the herbaceous bracts, hairy throughout ; the capsule cylindrical, ascending, twice as long as the calyx; fruit-stalks about as long as the calyx. This is a common
plant in fields and on banks, flowering from April to September. The other British species are a triviale, common in fields ; C. semidec andrurn, found in dry places : C. atrorirens, inhabiting sandy places and rocks near the sea ; C. pumilum, found only near Croydon in Surrey ; C. tetrandrum, found at Tynemouth and Shetland; C. lati folium, a rare plant ; and C. arvense, abundant in chalky and gravelly places.
A few of the species, ss C. tomentosum, C. grandiflorum, and C. Dahunicum are worth cultivating as border flowers. C. latifoliurn, C. alpinum, and C. glariale are adapted for growing on reck-work, or in small pots, when they should be placed in a mixture of loam, sand, and peat. They require the same general treatment as most hardy plants. The annual species may be propagated by sowing seed in an open border in the spring ; the perennial, by dividing the plants at the root.
(Don, Gardener's Dictionary ; Babington, Manual.)