fern ally vs quillwort

fern ally and quillwort both are nouns.

Word	Noun	Adjective	Verb	Adverb
fern ally	Yes	No	No	No
quillwort	Yes	No	No	No

As nouns, quillwort is a hyponym of fern ally; that is, quillwort is a word with a more specific, narrower meaning than fern ally:

fern ally: pteridophytes of other classes than Filicopsida
quillwort: any of several spore-bearing aquatic or marsh plants having short rhizomes and leaves resembling quills; worldwide except Polynesia

Other hyponyms of fern ally include whisk fern, horsetail, club-moss, club moss, lycopod.

fern ally (noun)	quillwort (noun)
pteridophytes of other classes than Filicopsida	any of several spore-bearing aquatic or marsh plants having short rhizomes and leaves resembling quills; worldwide except Polynesia