The lichen genus Physcia in North America
By: by John W. Thomson.  With 49 photographs on 25 plates and 37 distribution maps.
Series: Beihefte zur Nova Hedwigia, 7; Nova Hedwigia -- Heft 7.
Publisher: J. Cramer
Published: 1963
Place of publication: Weinheim
Language: eng
Number of pages: 172
Subjects: Lichens -- North America
Description: Explains what species are, how they become extinct, and the effect of extinction on the ecology, and surveys endangered species of plants and animals and possible solutions.