hornwort


horn·wort

noun \-ˌwərt, -ˌwrt\

Definition of HORNWORT

:  any of a genus (Ceratophyllum of the family Ceratophyllaceae) of rootless thin-stemmed aquatic monoecious herbs with female flowers having a single carpel

First Known Use of HORNWORT

circa 1805

hornwort

noun    (Concise Encyclopedia)

Any member of six to seven genera of creeping annual or perennial plants of the class Anthocerotopsida. Hornworts usually grow on damp soils or on rocks in tropical and warm temperate regions. The gametophyte typically is a flattened structure covered with small irregular lobes; the sporophyte forms a tapered cylinder (see alternation of generations). Rhizoids (rootlike structures) on the undersurface anchor the plant. Cavities in the gametophyte sometimes contain colonies of the cyanobacterium Nostoc (see cyanobacteria; nostoc). Hornworts have a region of continuous growth at the base of the sporophyte and a large, irregular foot. The stalk that attaches the foot to the spore-bearing capsule in liverworts is absent in hornworts.

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