promycelium vs basidium

promycelium and basidium both are nouns.

Word	Noun	Adjective	Verb	Adverb
promycelium	Yes	No	No	No
basidium	Yes	No	No	No

As nouns, basidium is a hypernym of promycelium; that is, basidium is a word with a broader meaning than promycelium:

promycelium: the basidium of various fungi
basidium: a small club-shaped structure typically bearing four basidiospores at the ends of minute projections; unique to basidiomycetes

promycelium (noun)	basidium (noun)
the basidium of various fungi	a small club-shaped structure typically bearing four basidiospores at the ends of minute projections; unique to basidiomycetes