[proh-thal-uh s]

noun, plural pro·thal·li [proh-thal-ahy] /proʊˈθæl aɪ/. Botany.

Origin of prothallus

From New Latin, dating back to 1850–55; see origin at pro-2, thallus Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for prothallus

Historical Examples of prothallus

  • With L. inundatum, however, the prothallus is green and leaf-like.

    How to Know the Ferns

    S. Leonard Bastin

  • Malic acid has, however, been discovered to be present in the prothallus as a whole.

    How to Know the Ferns

    S. Leonard Bastin

  • On the under side of the prothallus two kinds of organs appear (Fig. 510).

  • The prothallus is a small underground body destitute of chlorophyll.

    How to Know the Ferns

    S. Leonard Bastin

  • Upon the prothallus, or somewhat sunken in it, the sexual organs appear.

    The Nursery Book

    Liberty Hyde Bailey

British Dictionary definitions for prothallus


prothallium (prəʊˈθælɪəm)

noun plural -li (-laɪ) or -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 Formsprothallic or prothallial, adjective

Word Origin for prothallus

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 Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

prothallus in Science



Plural prothalli (prō-thălī)

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 © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.