Stemonitis, large genus of true slime molds (class Myxomycetes; q.v.) typical of the order Stemoniales. The species bear rusty to black spores on tiny featherlike fruiting bodies (sporangia), within an intricate network of threads (capillitium) arising from the stalk. The genus is a favourite textbook example of slime molds, including as it does some of the most beautiful fruiting bodies among the myxomycetes.