Argemone mexicana vs argemone

Argemone mexicana and argemone both are nouns.

Word	Noun	Adjective	Verb	Adverb
Argemone mexicana	Yes	No	No	No
argemone	Yes	No	No	No

As nouns, argemone is a hypernym of Argemone mexicana; that is, argemone is a word with a broader meaning than Argemone mexicana:

Argemone mexicana: annual herb with prickly stems and large yellow flowers; southern United States to West Indies and Mexico
argemone: any plant of the genus Argemone having large white or yellow flowers and prickly leaves and stems and pods; chiefly of tropical America

Other hypernyms of Argemone mexicana include devil's fig, prickly poppy, white thistle.

Argemone mexicana (noun)	argemone (noun)
annual herb with prickly stems and large yellow flowers; southern United States to West Indies and Mexico	any plant of the genus Argemone having large white or yellow flowers and prickly leaves and stems and pods; chiefly of tropical America