“+ noun
Usage: capitalized
Etymology: New Latin, from prot- + Greek siphōn siphon, tube, pipe
: a genus (the type of the family Protosiphonaceae) of unicellular multinucleate freshwater green algae consisting of a single form ( P. botryoides ) that is broadly tubular or more or less balloon-shaped and grows often confusingly mingled with Botrydium attached to mud by a single rarely branching rhizoid
• pro·to·siphonaceous “+ adjective