Mouse-ear \Mouse"-ear`\, n. (Bot.)
   (a) The forget-me-not (Myosotis palustris) and other species of the same genus.
   (b) A European species of hawkweed (Hieracium Pilosella).

Mouse-ear chickweed, a name of two common species of chickweed (Cerastium vulgarium, and C. viscosum).

Mouse-ear cress, a low cruciferous herb (Sisymbrium Thaliana). All these are low herbs with soft, oval, or obovate leaves, whence the name.

Source: Webster's Revised Unabridged Dictionary (1913)