Bracken fern rhizome, light micrograph

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Bracken fern rhizome. Polarized light micrograph of a cross-section through a rhizome from a bracken fern (Pteris aquilinum). The outer layer (yellow-green) consists of supporting fibers. Inside the stem are several meristeles, areas of vascular tissue. The outer layer of each meristele is an endoderm of single cells (dark brown). Below these are the pericycle and phloem cells (lighter brown). At the center of the meristeles is a lattice of xylem tissue. The phloem transports nutrients, while the xylem transports water and minerals. Magnification: x20 when printed at 10 centimeters across.

Dr. Keith Wheeler / Science Source

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