pileorhiza

from The Collaborative International Dictionary of English v.0.48

Pileorhiza \Pi`le*o*rhi"za\, n.; pl. {Pilorhiz[ae]}. [NL., fr.
   Gr. ? a cap + ? root.] (Bot.)
   A cap of cells which covers the growing extremity of a root;
   a rootcap.
   [1913 Webster]