protospore
/ˈprəʊtə(ʊ)spɔː/noun
1 Mycology. Originally: an early stage in fungal spore development believed to be analogous to the prothallus in ferns. In later use: specifically a uninucleate segment formed by the cleavage of a multinucleate mass of cytoplasm from which the spore or sporangium develops.
2 Biology. In a slime mould: a uninucleate segment of a multinucleate fruiting body from which the spore develops.
Origin
Mid 19th century; earliest use found in Mordecai Cooke (1825–1914), naturalist and mycologist. From proto- + spore.