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[proh-thal-ee-uh m] /proʊˈθæl i əm/
noun, plural prothallia
[proh-thal-ee-uh] /proʊˈθæl i ə/ (Show IPA)
Botany. the gametophyte of ferns and related plants.
the analogous rudimentary gametophyte of seed-bearing plants.
1855-60; < Neo-Latin < Greek pro- pro-2 + thallíon, diminutive of thallós young shoot; see -ium
Related forms
prothallial, prothallic, prothalline
[proh-thal-een, -ahyn] /proʊˈθæl in, -aɪn/ (Show IPA),
prothalloid, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for prothallium


noun (pl) -li (-laɪ), -lia (-lɪə)
(botany) the small flat free-living gametophyte that bears the reproductive organs of ferns, horsetails, and club mosses. It is either a green disc on the soil surface or it is colourless and subterranean
Derived Forms
prothallic, prothallial, adjective
Word Origin
C19: from New Latin, from pro- before + Greek thallus a young shoot
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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Encyclopedia Article for prothallium

the small, green, heart-shaped structure (gametophyte) of a fern that produces both male and female sex cells (gametes). The prothallium forms from a spore. After fertilization, a young sporophyte plant develops; it consists of a primary root, primary leaf, the rudiment of a new stem, and an organ, called a foot, that absorbs food from the gametophyte.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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