Physostigma vs plant genus

Physostigma and plant genus both are nouns.

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

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

Physostigma (noun)	plant genus (noun)
calabar beans (Physostigma)	a genus of plants