Terrestrial epiphytes comprise a taxonomically and morphologically diverse range of relatively large vascular plants (notably bromeliads, orchids, and ferns), and small nonvascular bryophytes (mosses and liverworts), lichens, and free-living algae. Growth forms include creepers, mats, brackets, nests, pendants, and shrubs. Most terrestrial epiphytes are self-contained on the bark or branches of their host, except for hemiepiphytes, which have roots reaching down to the ground. Not considered here are the mistletoes, which are parasitic, and the vines or lianas, which although using other plants for physical support do not have a crown attached to the host.
Aquatic epiflora are composed of red, green, and brown algae, and various other photosynthetic microorganisms. In freshwaters, microscopic, mostly unicellular, periphyton (or 'aufwuchs') dominate, while in the ocean macroalgae (seaweeds) are also important. Periphyton grows in thin films, while macroalgal epiphytes take encrusting, sheetlike, or branching forms, the latter two usually attached to their host by a small discoid holdfast or penetrative rhizoids.
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