CONFERVA
conferva
(noun) any of various algae of the genus Tribonema; algae with branching filaments that form scum in still or stagnant fresh water
Source: WordNet® 3.1
Etymology
Noun
conferva (plural confervas or confervae)
An unbranched slender green freshwater alga.
Source: Wiktionary
Con*fer"va, n.; pl. Confervæ. Etym: [L., a kind of water plant. See
Comfrey.] (Bot.)
Definition: Any unbranched, slender, green plant of the fresh-water algae.
The word is frequently used in a wider sense.
Source: Webster’s Unabridged Dictionary 1913 Edition