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A ray appears diagonally, from top left to bottom middle. Medullary rays , also known as vascular rays or pith rays , are cellular structures found in some species of wood . They appear as radial planar structures, perpendicular to the growth rings, which are visible to the naked eye.
Pith is composed of soft, spongy parenchyma cells, which in some cases can store starch. In eudicotyledons, pith is located in the center of the stem. In monocotyledons, it extends only into roots. [1] The pith is encircled by a ring of xylem; the xylem, in turn, is encircled by a ring of phloem.
Parenchyma forms the "filler" tissue in the soft parts of plants, and is usually present in cortex, pericycle, pith, and medullary rays in primary stem and root. Collenchyma cells have thin primary walls with some areas of secondary thickening. Collenchyma provides extra mechanical and structural support, particularly in regions of new growth.
During secondary growth, cells of medullary rays, in a line (as seen in section; in three dimensions, it is a sheet) between neighbouring vascular bundles, become meristematic and form new interfascicular cambium (between vascular bundles).
In a vascular plant, the stele is the central part of the root or stem [1] containing the tissues derived from the procambium. These include vascular tissue, in some cases ground tissue and a pericycle, which, if present, defines the outermost boundary of the stele.
In anatomy, a medullary ray (Ferrein's pyramid) is the middle part of a cortical lobule (or renal lobule). Each consists of a group of nephrons in the renal cortex . [ 1 ] Their name is potentially misleading, as "medullary" refers to their destination, not their location.
From January 2008 to December 2012, if you bought shares in companies when Reuben V. Anderson joined the board, and sold them when he left, you would have a -7.1 percent return on your investment, compared to a -2.8 percent return from the S&P 500.
Cross-section of a flax plant stem: 1. Pith 2. Protoxylem 3. Xylem I 4. Phloem I 5. Sclerenchyma 6. Cortex 7. Epidermis. In botany, a cortex is an outer layer of a stem or root in a vascular plant, lying below the epidermis but outside of the vascular bundles. [1]