Medical Dictionary

A major group of lower plants that comprises, usually, photosynthetic plants of extremely varied morphology and physiology, and that is commonly considered to be a heterogeneous assemblage. They are freshwater and marine, terrestrial and subterranean; some are neustonic (living at the interface of water and the atmosphere). They live in various protozoa and within other plants. Among the vectors of aquatic algae are water movements (tides and currents), wind, ships, beetles, aquatic birds, etc. They live also in soil and on soil surfaces, on long-persistent snows, and in Antarctic rocks. Thermophilic algae inhabit hot springs. (From Webster, 3d ed; from Bold & Wynne, Introduction to the Algae, 2d ed, pp1-6)