Webster’s Revised Unabridged Dictionary · 1913
Hydrorhiza
Hy′dro·rhi′za, n.; pl. L. Hydrorhizæ (#), E. Hydrorhizas (#). [NL., fr. E. hydra + Gr. ῥίζα a root.] (Zoöl.) The rootstock or decumbent stem by which a hydroid is attached to other objects. See Illust. under Hydroidea.