\Hy`dro*rhi"za\, n.; pl. L. {Hydrorhiz[ae]}, E.
{Hydrorhizas}. [NL., fr. E. hydra + Gr. ? a root.] (Zo["o]l.)
The rootstock or decumbent stem by which a hydroid is
attached to other objects. See Illust. under {Hydroidea}.