What is "pith"

Pith \Pith\, n. [AS. pi?a; akin to D. pit pith, kernel, LG. peddik. Cf. Pit a kernel.]

1. (Bot.) The soft spongy substance in the center of the stems of many plants and trees, especially those of the dicotyledonous or exogenous classes. It consists of cellular tissue.

2. 1. (Zo["o]l.) The spongy interior substance of a feather.

   2. (Anat.) The spinal cord; the marrow.

3. Hence: The which contains the strength of life; the vital or essential part; concentrated force; vigor; strength; importance; as, the speech lacked pith.

   Enterprises of great pith and moment.
   --Shak.

   Pith paper. Same as Rice paper, under Rice.

Pith \Pith\, v. t. (Physiol.) To destroy the central nervous system of (an animal, as a frog), as by passing a stout wire or needle up and down the vertebral canal.

Old English piþa "pith of plants," also "essential part," from West Germanic *pithan- (cognates: Middle Dutch pitte, Dutch pit, East Frisian pit), a Low German root of uncertain origin. Figurative sense was in Old English. Pith helmet (1889, earlier pith hat, 1884) so called because it is made from the dried pith of the Bengal spongewood.

"to kill by piercing the spinal cord," 1805, from pith (n.). Related: Pithed; pithing.

n. 1 The soft, spongy substance in the center of the stems of many plants and trees. 2 The spongy interior substance of a feather. 3 The spinal cord; the marrow. 4 (context figuratively English) The essential or vital part. vb. 1 (context transitive English) To extract the pith from (a plant stem or tree). 2 (context transitive English) To kill (especially cattle or laboratory animals) by cutting or piercing the spinal cord.

1. n. soft spongelike central cylinder of the stems of most flowering plants

2. the choicest or most essential or most vital part of some idea or experience; "the gist of the prosecutor's argument"; "the heart and soul of the Republican Party"; "the nub of the story" [syn: kernel, substance, core, center, essence, gist, heart, heart and soul, inwardness, marrow, meat, nub, sum, nitty-gritty]

Pith, or medulla, is a tissue in the stems of vascular plants. Pith is composed of soft, spongy parenchyma cells, which store and transport nutrients throughout the plant. In eudicots, pith is located in the center of the stem. In monocots, it extends also into flowering stems and roots. The pith is encircled by a ring of xylem; the xylem, in turn, is encircled by a ring of phloem.

While new pith growth is usually white or pale in color, as the tissue ages it commonly darkens to a deeper brown color. In trees pith is generally present in young growth, but in the trunk and older branches the pith often gets replaced - in great part - by xylem. In some plants, the pith in the middle of the stem may dry out and disintegrate, resulting in a hollow stem. A few plants, such as walnuts, have distinctive chambered pith with numerous short cavities (See image at middle right). The cells in the peripheral parts of the pith may, in some plants, develop to be different from cells in the rest of the pith. This layer of cells is then called the perimedullary region of the pithamus. An example of this can be observed in Hedera helix, a species of ivy.

The term pith is also used to refer to the pale, spongy inner layer of the rind - more properly called mesocarp or albedo - of citrus fruits (such as oranges) and other hesperidia. The word comes from the Old English word piþa, meaning substance, akin to Middle Dutch pitt, meaning the pit of a fruit.

The pith of the sola or other similar plants is used to make the pith helmet.

The pith of the sago palm, although highly toxic to animals in its raw form, is an important human food source in Melanesia and Micronesia by virtue of its starch content and its availability. There is an easy, primitive process of starch extraction from sago pith that leaches away a sufficient amount of the toxins and thus only the starch component is consumed. The form of the starch after processing is similar to tapioca.