Stem. - Clothed with soft hairs. Leaves. - Alternate, hairy, the upper ones lance-shaped, clasping somewhat by a rounded or heart-shaped base. Flowers. - Purplish-red, growing in a curved raceme-like cluster which straightens as the blossoms expand. Calyx. - Five-parted. Corolla'. - Funnel-form, five-lobed. Stamens. - Five. Pistil. - One. Fruit. - A large nutlet roughened with barbed or hooked prickles.

This coarse plant, whose disagreeable odor strongly suggests mice, is not only a troublesome weed in pasture-land but a special annoyance to wool-growers, as its prickly fruit adheres with pertinacity to the fleece of sheep. Its common name is a translation of its generic title and refers to the shape and texture of the leaves. The dull red flowers appear in summer.