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[in-doo-zee-uh m, -zhee-uh m, -dyoo-] /ɪnˈdu zi əm, -ʒi əm, -ˈdyu-/
noun, plural indusia
[in-doo-zee-uh, -zhee-uh, -dyoo-] /ɪnˈdu zi ə, -ʒi ə, -ˈdyu-/ (Show IPA)
Botany, Mycology. any of several structures having a netlike or skirtlike shape, as the membranous overgrowth covering the sori in ferns.
Anatomy, Zoology.
  1. an enveloping layer or membrane.
  2. a thin layer of gray matter on the corpus callosum.
Origin of indusium
1700-10; < New Latin; Latin: kind of tunic, perhaps < Greek éndys(is) dressing, dress (endý(ein) to put on + -sis -sis) + Latin -ium, for Greek -ion noun suffix
Related forms
indusial, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for indusia
Historical Examples
  • The sori have indusia, but this is hidden by the margin of the pinnules, which are recurved.

    How to Know the Ferns S. Leonard Bastin
  • The indusia are soon thrown off when the spore cases start to develop.

    How to Know the Ferns S. Leonard Bastin
  • Like all the Polypodies the clusters of sporangia have no indusia.

    How to Know the Ferns S. Leonard Bastin
  • The sori are quite naked, no indusia being present at any time.

    How to Know the Ferns S. Leonard Bastin
  • The indusia appear as little whitish scales on the back of the veins.

    Beautiful Ferns Daniel Cady Eaton
  • Sporangia near or on the margin of the segments, the reflexed portions of which serve as indusia.

    The Fern Lover's Companion George Henry Tilton
  • The indusia of the areoles next the midrib are also often bent at an angle, and the two portions plainly united.

    Beautiful Ferns Daniel Cady Eaton
  • The two plants might be difficult to distinguish were it not for the difference in their indusia.

    How to Know the Ferns Frances Theodora Parsons
  • In systematic botanies the indusia play an important part in determining genera.

    How to Know the Ferns Frances Theodora Parsons
  • With the disappearance of the indusia the sori tend to spread over the whole surface of the back of the frond.

    How to Know the Ferns S. Leonard Bastin
British Dictionary definitions for indusia


noun (pl) -sia (-zɪə)
a membranous outgrowth on the undersurface of fern leaves that covers and protects the developing sporangia
an enveloping membrane, such as the amnion
Derived Forms
indusial, adjective
Word Origin
C18: New Latin, from Latin: tunic, from induere to put on
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
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indusia in Science
  (ĭn-d'zē-əm, -zhē-)   
Plural indusia
  1. A thin membrane covering the sorus of a fern. The indusium often shrivels away when spores are ready to be dispersed. Also called fruitcover.

  2. A cuplike structure fringed with hairs and located at the top of the style in flowers of the family Goodeniaceae (which includes the garden flowers lobelia and scaevola). Pollen is deposited into the indusium by the anthers of the same flower and, as the style grows, carried up for dispersal by pollinating insects.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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