fern genus vs genus

fern genus and genus both are nouns.

Word	Noun	Adjective	Verb	Adverb
fern genus	Yes	No	No	No
genus	Yes	No	No	No

As nouns, genus is a hypernym of fern genus; that is, genus is a word with a broader meaning than fern genus:

fern genus (noun)	genus (noun)
genera of ferns and fern allies	a general kind of something
	(biology) taxonomic group containing one or more species