Source : Webster's Revised Unabridged Dictionary (1913)

Alum root \Al"um root`\ (Bot.)
   A North American herb ({Heuchera Americana}) of the Saxifrage
   family, whose root has astringent properties.

Source : WordNet®

Heuchera americana
     n : plant with basal leaves mottled with white and flowers in
         lax panicles on erect stems [syn: {rock geranium}]