An annotated, vouchered checklist of the bryophytes of the California Channel Islands is presented, including the known distribution of each species across the eight islands. The bryoflora currently comprises 158 minimally ranked taxa. Fifty-nine mosses, two hornworts, and twenty-two liverworts are reported for the first time from the islands. Fifteen species previously reported from the archipelago are excluded based on new determinations and nomenclatural changes. The bryoflora includes two putative undescribed species in the Bryaceae, Plagiobryoides sp. from Santa Catalina Island and Gemmabryum sp. from Santa Rosa Island. Excluding these two putative new species, no new state records are reported. One species, Tortula californica, is listed by the California Native Plant Society at the 1B rank. Previous reports from the literature are catalogued and nomenclatural changes are noted. There are no island endemics, with the possible exception of the two putative undescribed species. The bryoflora is similar to that of the adjacent mainland, but the larger islands harbor disjunct populations of species from the wet forests of central and northern California that are absent on the adjacent mainland.

245 described species, two undescribed species and four varieties of moss are documented on the Plumas National Forest, California representing approximately 35% of the California moss flora. Nineteen species are new records for the Sierra Nevada mountain range of California. The high rainfall on the western slope of the forest and associated habitat conditions allow for many disjunct coastal species. Four species, Pohlia flexuosa Harv. in Hook., Schistidium subjulaceum H.H. Blom, Scopelophila ligulata (Spruce) Spruce, and Sphagnum angustifolium (Russow) C. Jensen in K. R. Tolf, were found new to California during this study. Five species, Gemmabryum vinosum J.R. Spence & Kellman, Homalothecium californicum Hedenäs, Huttunen, Shevock & D.R. Norris, Orthotrichum confusum R. Medina, F. Lara & Garilleti, Ptychostomum pacificum J.R. Spence & Shevock, and Schistidium splendens T.T. McIntosh, H. H. Blom, Toren & Shevock were recently described, partially using material collected as part of this study.

The moss flora of Lake County, California comprises of 300 species and one variety within 111 genera. This represents 44 percent of the California moss flora occupying an area less than one percent of the state land area. Six species, Bryum veronense De Notaris, Gemmabryum kunzei (Hornschuch) J.R. Spence, Schistidium flaccidum (De Notaris) Ochyra, Tortella alpicola Dixon, Trichodon cylindricus (Hedwig) Schimper, and Trichostomum brachydontium Bruch were documented as new for California. Four species, Acaulon mediterraneum Limpricht, Funaria convexa Spruce, Gymnostomum viridulum Bridel and Schistidium echinatum Ignatova & H.H. Blom, were documented as new records for the North American moss flora. During this study, thirteen species were described as new to science with at least one occurrence documented from Lake County: Didymodon californicus J.A. Jiménez, D.R. Toren & Shevock, D. eckeliae R.H. Zander, D. norrisii R.H. Zander, Gemmabryum vinosum J.R. Spence & Kellman, Grimmia serrana Muñoz, Shevock & D.R. Toren, G. torenii R.I. Hastings, Homalothecium californicum Hedenäs, Huttunen, D.H. Norris & Shevock, Imbribryum torenii J.R. Spence & Shevock, Orthotrichum persimile F. Lara, R. Medina & Garilleti, Ptychostomum pacificum J.R. Spence & Shevock, Schistidium splendens T.T. McIntosh, H.H. Blom, D.R. Toren & Shevock, S. squarrosum T.T. McIntosh, H.H. Blom, D.R. Toren & Shevock and Scleropodium occidentale B.E. Carter.