The Collaborative International Dictionary of English v.0.48:

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).
          [1913 Webster]

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

   Mouse-ear cress, a low cruciferous herb (Sisymbrium
      Thaliana). All these are low herbs with soft, oval, or
      obovate leaves, whence the name.
      [1913 Webster]