Xylaria polymorpha vs fungus

Xylaria polymorpha and fungus both are nouns.

Word	Noun	Adjective	Verb	Adverb
Xylaria polymorpha	Yes	No	No	No
fungus	Yes	No	No	No

As nouns, fungus is a hypernym of Xylaria polymorpha; that is, fungus is a word with a broader meaning than Xylaria polymorpha:

Xylaria polymorpha: the fruiting bodies of the fungi of the genus Xylaria
fungus: an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia

Xylaria polymorpha (noun)	fungus (noun)
the fruiting bodies of the fungi of the genus Xylaria	an organism of the kingdom Fungi lacking chlorophyll and feeding on organic matter; ranging from unicellular or multicellular organisms to spore-bearing syncytia