Pith

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The centre dark spot (about 1 mm diameter) in this yew wood is the pith

Elderberry shoot cut longitudinally to show the broad, solid pith (rough-textured, white) inside the wood (smooth, yellow-tinged). Scale in mm.

Walnut shoot cut longitudinally to show the chambered pith found in this genus. Scale in mm.

Pith is a substance that is found in vascular plants. It consists of soft, spongy parenchyma cells, and is located in the center of the stem in eudicots (both herbaceous and woody) and in the center of the roots in monocots. It is encircled by a ring of xylem (woody tissue), and outside that, a ring of phloem (bark tissue). In some plants the pith is solid, but for most it is soft. A few plants, such as walnuts, have distinctive chambered pith with numerous short cavities.

The word comes from the Old English word piþa, meaning substance, akin to Middle Dutch pit, meaning the pit of a fruit.

The pith varies in diameter from about 0.5 mm to 6-8 mm in solid pith. Freshly grown pith in young new shoots is typically white or pale brown, commonly darkening with age. In woody plants (trees, shrubs), the pith becomes surrounded by successive annual layers of wood; it may be very inconspicuous but is always present at the center of a trunk or branch. 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. One example is Hedera helix.

The pith of the sola or other similar plants is used to make the pith helmet ^[1].

The pith of some plants, such as sago, is edible to humans.

The inner rind or albedo of hesperidium is also called pith.

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