Salix sitchensis vs genus Salix

Salix sitchensis and genus Salix both are nouns.

Word	Noun	Adjective	Verb	Adverb
Salix sitchensis	Yes	No	No	No
genus Salix	Yes	No	No	No

Salix sitchensis (noun)	genus Salix (noun)
small shrubby tree of western North America (Alaska to Oregon)	a large and widespread genus varying in size from small shrubs to large trees: willows