genus Martynia vs plant genus

genus Martynia and plant genus both are nouns.

Word	Noun	Adjective	Verb	Adverb
genus Martynia	Yes	No	No	No
plant genus	Yes	No	No	No

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

genus Martynia (noun)	plant genus (noun)
in some classifications includes the unicorn plants	a genus of plants