Cerastium diffusum the fourstamen chickweed or sea mouse-ear, is a species in the genus Cerastium, belonging to the Caryophyllaceae family. It is an annual or biannual herb, 3 to 15 cm.high, occurring in western Europe in the seacoast areas. The flowers have 4, or seldom 5 petals, 4 or 5 stamen appearing between March and May (III-V). The leaves are linial, ong and spade-shaped. The fruit petioles stand straight up.