Four species of mosses, all in the genusOrthotrichum; 1 species of hepatics; and 16 species of lichens compose the foliicolous bryophyte and lichen flora ofThuja plicataL. leaves in certain areas of western British Columbia. This is the first report of foliicolous mosses and hepatics for North America, north of the tropical and subtropical regions of the southeastern United States. The taxonomy of the four species ofOrthotrichumis discussed and a key given differentiating the species.All of the species that have been found onThujaleaves except perhapsCatillaria bouteilleiare facultative foliicolous species and occur on leaves, only in scattered areas of northwestern North America. Two taxa of lichens,Catillaria bouteillei(Desm.) Zahlbr. andCetrelia cetrarioides(Del. ex Duby) W. Culb. & C. Culb. (perlatolic acid strain) are reported as new to Canada.