Book Chapters

1965. Plant geography in the southern Rocky Mountains. [in] The Quaternary of the United States. ed. H. E. Wright, Jr. & David G. Frey), pp. 453–468.

1966. Lichenology and bryology in the Galápagos Islands, with check lists of the lichens and bryophytes thus far reported. Pp. 190–200 [in] The Galápagos (Robert I. Bowman, ed.). Univ. California Press.

1971. Das Pflanzenkleid [Vegetation], pp. 10–122, [in] The Grand Canyon. Kümmerly & Frey, Bern. (German and English versions)

1977. Environmental modification and lichen taxonomy. Chapter 2, pp. 9–29 [in] Seaward, M. R. D., ed. Lichen Ecology. Academic Press.

1984. Lichens and Bryophytes. Chapter 5, pp. 71–84, [in] Key Environments, Galápagos. Pergamon Press, Oxford.

1986. Effects on cryptogamic vegetation (lichens, mosses, and liverworts) [with Hans Beck]. pp. 343–361, [in] El Niño in the Galápagos Islands: the 1982–1983 Event. Gary Robinson & Eugenia M. del Pino, eds. Charles Darwin Foundation, Quito.

2006. Balsamorhiza, Scabrethia, Wyethia, Agnorhiza, pp. 93–105; Helianthella, pp. 114–117, [in] Flora of North America. Vol. 21, Asteraceae, Part 3. Flora of North America Editorial Committee.

2007. Oreas martiana (bryophytes). [in] Flora of North America, Bryophytes, Vol. 27.

2008. Leptopterigynandrum austro-alpinum. [in] Flora of North America, Vol 28 [in progress]