horse grain vs leguminous plant

horse grain and leguminous plant both are nouns.

Word	Noun	Adjective	Verb	Adverb
horse grain	Yes	No	No	No
leguminous plant	Yes	No	No	No

As nouns, leguminous plant is a hypernym of horse grain; that is, leguminous plant is a word with a broader meaning than horse grain:

horse grain: twining herb of Old World tropics cultivated in India for food and fodder; sometimes placed in genus Dolichos
leguminous plant: an erect or climbing bean or pea plant of the family Leguminosae

Other hypernyms of horse grain include legume.

horse grain (noun)	leguminous plant (noun)
twining herb of Old World tropics cultivated in India for food and fodder; sometimes placed in genus Dolichos	an erect or climbing bean or pea plant of the family Leguminosae