CERASTIUM, in botany, a genus of the decandria pentagynia class. The calix has five leaves; the petals are bifid; and the capsule is unilocular, and opens at the top. There are sixteen species, seven of which are natives of Britain, viz. the vulgatum, or narrow-leaved mouse-ear chickweed; the viscosum, or broad-leaved mouse-ear chickweed; the femidecandrium, or least mouse-ear chickweed; the arvense, or corn mouse-ear chickweed; the alpinum, or mountain mouse-ear chickweed; the tomentosum, or woolly mouse-ear chickweed; and the aquaticum, or marsh mouse-ear chickweed.