water-chickweed

from The Century Dictionary.

• noun A small, smooth, and green tufted herb, Montia fontana, found throughout Europe, in northern Asia, from arctic America down the west coast to California, and in the Andes to their southern extremity. Also blinking-chickweed (which see).
• noun A name for Callitriche verna and Stellaria (Malachium) aquatica.