nemathecium

noun, plural nem·a·the·ci·a [nem-uh–thee-shee-uh, -see-uh] /ˌnɛm əˈθi ʃi ə, -si ə/.

1. a wartlike protuberance on the thallus of certain red algae, containing tetraspores, antheridia, or cystocarps.