'Prothalli' definitions:

Definition of 'Prothalli'

From: GCIDE

Prothallus \Pro*thal"lus\, n.; pl. Prothalli. [NL., fr. Gr. ? before + ? a young shoot.] (Bot.) The minute primary growth from the spore of ferns and other Pteridophyta, which bears the true sexual organs; the oophoric generation of ferns, etc. [1913 Webster]