A field guide to the ferns : and their related families of northestern and central north america / by Boughton Cobb. Cob, boughton. Ferns -- North America -- Identification. Fougères -- Amérique du Nord -- Identification. 587.31 COF includes bibliographical references and index. Cambridge : Boughton mifflin company, c1956. c1956. 1965 Text xviii, 281p. : eng the peterson field guide series.