A Grammatical Dictionary of Botanical Latin

Pileorhiza, “the cap of a root; a membranous hood found at the end of the roots of Nuphar and other plants, and distinct from the spongiole” (Lindley); “the root-cap; a hood at the extremity of the root” (Jackson) [> Gk. “pileos, Lat. pileus, a cap + rhiza, a root” (Jackson)]; see pileus; see root-cap; see spongiole.

NOTE: ‘hood’ = calyptra,-ae (s.f.I), q.v.: “a term proposed by Van Tieghem and Douliot for that portion of the root-cap in lateral roots which belongs strictly to the root-system” (Jackson).

Calyptrogen, “the layer of cells from which the rootcap originated” (WIII); see -gen.

The true root: “the outer single layer of cells, known as the dermatogen, in addition to giving rise to the epidermis, forms the cap-shaped mass of tissue called the root-cap or pileorhiza, by which the growing apex of the root is always clothed.

“All roots and the branches of a root grow in length in a similar manner to the radicle as above described; hence roots do not grow throughout their entire length like stems, but only within their extremities, which are continually pushed forward and renewed. Thus the apex of the root is always clothed by a layer of denser tissue which is commonly known as the root-cap. All the branches of a root are likewise terminated by a similar cap” (Bentley).

“These cap-like coverings at the extremities of the root were formerly regarded as special organs and called spongioid or spongelets, under the idea that they absorbed fluid for the use of the plant, in the same manner as a sponge sucks up water. But it will be seen from the above description of the growth of roots that such structures have no existence” (Bentley).