the small flat free-living gametophyte that bears the reproductive organs of ferns, horsetails, and club mosses. It is either a green disc on the soil surface or it is colourless and subterranean
Derived forms
prothallic (proˈthallic) or prothallial (proˈthallial)
adjective
Word origin
C19: from New Latin, from pro- before + Greek thallos a young shoot