Gray's Manual of botany :
a handbook of the flowering plants and ferns of the central and northeastern United States and adjacent Canada.

APA Citation

Gray, A., Fernald, M. Lyndon. (1950). Gray's Manual of botany: a handbook of the flowering plants and ferns of the central and northeastern United States and adjacent Canada. 8th (centennial) ed. / New York: American Book Co..

MLA Citation

Gray, Asa, 1810-1888, and Merritt Lyndon Fernald. Gray's Manual of Botany: a Handbook of the Flowering Plants And Ferns of the Central And Northeastern United States And Adjacent Canada. 8th (centennial) ed. / New York: American Book Co., 1950.