What is "ulmin"

Humin \Hu"min\, n. [L. humus the earth, ground.] (Chem.) A bitter, brownish yellow, amorphous substance, extracted from vegetable mold, and also produced by the action of acids on certain sugars and carbohydrates; -- called also humic acid, ulmin, gein, ulmic or geic acid, etc.

n. (context organic compound English) A brown amorphous substance found in decaying vegetation.