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[proh-thal-uh s] /proʊˈθæl əs/
noun, plural prothalli
[proh-thal-ahy] /proʊˈθæl aɪ/ (Show IPA).
Origin of prothallus
1850-55; < New Latin; see pro-2, thallus Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for prothallus


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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prothallus in Science
Plural prothalli (prō-thāl'ī)
The gametophyte of homosporous ferns and some other plants. Prothalli have chlorophyll for photosynthesis, but they are not differentiated into roots, stems, or leaves. They are usually small, flat, and delicate. Prothalli develop from germinated spores, and they bear both archegonia for producing eggs and antheridia for producing sperm. See more at alternation of generations.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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