Indusium


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Related to Indusium: pollen grain, indehiscent, strobilus, sporophyll, indusium griseum

indusium

[in′dü·zē·əm]
(anatomy)
A covering membrane such as the amnion.
(botany)
An epidermal outgrowth covering the sori in many ferns.
(mycology)
The annulus of certain fungi.

Indusium

 

a small process on the leaf surface of ferns that covers the clusters of sporangia (sori). Indusia develop mainly from the leaf epidermis, from the placenta (on which the sporangia sit), or from the curled edge of the leaf.

References in periodicals archive ?
The dorsal extension of the hippocampus (the indusium griseum--also called the supracallosal gyrus) comprises two thin grey-matter strips that overlay the corpus callosum; it is a vestigial structure of unknown function in the postnatal brain.
Indusium absent; stem diameter 1-4 mm; rachis winged throughout 2.
ATHYRIUM {eh-THIR-ee-um} Roth 1799 * Lady Ferns * (Greek athyros, doorless; sporangia tardily pushing open margin of indusium.
5-2 mm Blade degree of division pinnate shape ovate to deltoid apex attenuate, pinnatifid base truncate, sometimes obtuse size (length X width) 13-33 X 12-28 cm texture herbaceous Rachis color greenish indumentum brownish to blackish filiform scales and scarce pluricellular hairs Pinnae shape lanceolate orientation with ascending respect to rachis apex acute to attenuate petiolule petiolulate margin denticulate size (length X width) 7-12 X 1-2 cm number of pairs 6-11 Venation veins 2-forked Sori shape linear number of pairs 5-8 length 4-10 mm position medial Indusium color light brown margin entire width 0.
1 mm long scattered acicular hairs, sometimes laminar hairs emerging through the sinus of the indusium appear to be part of the indusium proper; spores echinulate.
Yesilyurt (2005) segregated this species based on its filiform segments, pinnate division, and crenulate indusium margins.
2 mm wide, strongly imbricate, spreading laterally, with erosedentate margins, not ciliate, brown proximally, paleaceous distally, attenuate to hair-like apices; ultimate segments round to elliptical, the largest 1-2 mm wide, with coarse, contorted, whitish or translucent hairs adaxially and occasional hairs and narrow scales abaxially; leaf margins recurved, forming a weakly differentiated marginal false indusium to 0.
From these materials, we diagnose the species as having ferruginous stem scales that contrast with the large basal petiole-scales, which have atropurpureous centers and rufous edges; long, delicate petiole-scale cilia; 2-pinnate laminae that lack a bulbil; lanceolate rachis scales that are either entirely rufous or bicolorous with dark centers; long-lanceolate, rufous pinna-rachis scales; serrate pinnules with strongly developed spinules; glandular trichomes on both sides of the pinnules, and no true indusium (Figs.