Pith

Pith, also called medulla, is the spongy tissue of soft parenchyma cells found in the stems of vascular plants, occupying the center of the stem in eudicotyledons and extending into the roots in monocotyledons. It is encircled by a ring of xylem, itself surrounded by phloem, and often stores starch; fresh pith is usually white or pale, darkening to brown with age, and in some plants it dries into a hollow or chambered cavity. Beyond its role in plant anatomy it has practical uses: sago pith is processed into a starch food source in Melanesia and Micronesia, pith wood is used by watchmakers to clean delicate parts, dried rush pith was historically burned for home lighting, and pith wood was once the material used to make pith helmets. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/