indusium vs natural covering

indusium and natural covering both are nouns.

Word	Noun	Adjective	Verb	Adverb
indusium	Yes	No	No	No
natural covering	Yes	No	No	No

As nouns, natural covering is a hypernym of indusium; that is, natural covering is a word with a broader meaning than indusium:

indusium: a membrane enclosing and protecting the developing spores especially that covering the sori of a fern
natural covering: a natural object that covers or envelops

Other hypernyms of indusium include cover, covering.

indusium (noun)	natural covering (noun)
a membrane enclosing and protecting the developing spores especially that covering the sori of a fern	a natural object that covers or envelops