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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 indusium
Historical Examples
  • The indusium arises from a vein to which the sorus is attached.

    How to Know the Ferns S. Leonard Bastin
  • The sorus is circular and is covered with an indusium which is notched or kidney-shaped.

    How to Know the Ferns S. Leonard Bastin
  • Thus it is proper to describe the shape of the indusium as peltate.

    How to Know the Ferns S. Leonard Bastin
  • The sori are narrow, and when young are covered with an indusium.

    How to Know the Ferns S. Leonard Bastin
  • The sori are quickly confluent, and all trace of the indusium is soon lost.

    Beautiful Ferns Daniel Cady Eaton
  • The indusium is orbicular-reniform, and almost always smooth.

    Beautiful Ferns Daniel Cady Eaton
  • Rarely the sinus is so deep that the indusium at last becomes divided.

    Beautiful Ferns Daniel Cady Eaton
  • indusium, the shield or covering of a fruit-dot of a Fern, 159.

  • indusium fixed by its outer margin to a veinlet and opening on the inner side.

    The Fern Lover's Companion George Henry Tilton
  • indusium straight or rarely curved, fixed lengthwise on the upper side of a fertile veinlet, opening toward the midrib.

    The Fern Lover's Companion George Henry Tilton
British Dictionary definitions for indusium


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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indusium 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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