Prothallus is seen in:
In pteridophytes (Selaginella), spores germinate to give rise to inconspicuous, small but multicellular, free-living, mostly photosynthetic thalloid gametophytes called prothallus.
Polytrichum is a bryophyte.
Gnetum is a gymnosperm.
Oryza sativa (rice) is an angiosperm.