As nouns the difference between prothallus and protocorm
is that prothallus is a prothallium while protocorm is (botany) a tuberous mass of cells that is the embryonic form of orchids and club mosses.
prothallus
English
Noun
(prothalli)
A prothallium.
protocorm
English
Noun
(
en noun)
(botany) A tuberous mass of cells that is the embryonic form of orchids and club mosses
*
References
*OED (online) 2007