The Collaborative International Dictionary
Perichaetia
Perichaetium \Per`i*ch[ae]"ti*um\, n.; pl. Perich[ae]tia. [NL., fr. Gr. ? about + ? flowing hair, foliage.] (Bot.) Same as Perich[ae]th.
Wiktionary
perichaetia
n. (plural of perichaetium English)