2 MISC. PUBLICATION 42 3, U. S. DEPT. OF AGRICULTURE 



absence of such a publication, identification of plants collected in 

 Arizona is very difficult, requiring access to an extensive herbarium 

 and botanical library. Approximately two-thirds (67.2 percent) of 

 the total area of the State is controlled by the Federal Government, 

 48.2 percent being administered by the Indian Service, Forest Service, 

 National Park Service, and Fish and Wildlife Service, and 19 percent 

 being classified as vacant public land. Many of the native plants of 

 Arizona are economically important, and the scientific staffs of the 

 services mentioned, as well as of other branches of the Federal Govern- 

 ment, frequently require accurate identification of plants collected by 

 them. It therefore seems appropriate that the United States Depart- 

 ment of Agriculture should undertake publication of a flora of Arizona. 



COLLABORATORS 



Authorities on many difficult families and genera have contributed 

 treatments of their specialties, adding greatly to the value of this 

 publication. The writers are most grateful for the collaboration of 

 these botanists, whose names, and the group or subject contributed, 

 follow: 



Benson, Lyman, University of Arizona. Genus Ranunculus. 



Blake, S. F., Division of Plant Exploration and Introduction, Bureau of Plant 



Industry, United States Department of Agriculture. Family Compositae. 

 Epling, Carl, University of California at Los Angeles. Family Labiatae. 

 Ewan, Joseph, University of Colorado. Genus Delphinium. 

 Hermann, F. J., Division of Plant Exploration and Introduction, Bureau of 



Plant Industry, United States Department of Agriculture. Genus Juncus. 

 Hitchcock, C. Leo, University of Washington. Genus Draba. 

 Johnston, I. M., Arnold Arboretum, Harvard University. Family Boraginaceae. 

 Keck, David D., Carnegie Institution of Washington, Genus Penstemon. 

 Killip, Ellsworth P., Smithsonian Institution. Genus Passiflora (key). 

 Mathias, Mildred E., and Constance, Lincoln, University of California. Family 



Umbelliferae. 

 Maxon, William R., Smithsonian Institution. Ferns and fern allies. 

 McVaugh, Rogers, Division of Plant Exploration and Introduction, Bureau of 



Plant Industry, United States Department of Agriculture. Family Cam- 



panulaceae. 

 Morton, C. V., Smithsonian Institution. Genera Datura and Nicotiana (keys). 

 Muller, Cornelius H., Division of Plant Exploration and Introduction, Bureau of 



Plant Industry, United States Department of Agriculture. Genera Quercus 



and Choisya. 

 Munz, Philip A., Pomona College. Family Onagraceae. 



Rollins, Reed C, Dudley Herbarium, Stanford University. Genus Arabis. 

 Shreve, Forrest, Carnegie Institution of Washington. The vegetation of Arizona. 

 Stacey, J. W., California Academy of Sciences. Genus Car ex. 

 Svenson, H. K., Brooklyn Botanic Garden. Genus Eleocharis. 

 Swallen, Jason R., Division of Plant Exploration and Introduction, Bureau of Plant 



Industry, United States Department of Agriculture. Family Gramineae. 

 Wheeler, Louis C, University of Pennsylvania. Family. Euphorbiaceae. 

 Wherry, Edgar T., University of Pennsylvania. Genus Phlox. 

 Yuncker, T. G., DePauw University. Genus Cuscuta. 



The writers also wish to express their sincere appreciation of the 

 courteous assistance rendered by the curators of herbaria and members 

 of the botanical staff of the following institutions: National Her- 

 barium, Smithsonian Institution; the Forest Service, United States 

 Department of Agriculture; Gray Herbarium, Harvard University; 

 New York Botanical Garden; Field Museum; Missouri Botanical 

 Garden; Rocky Mountain Herbarium, University of Wyoming; Uni- 

 versity of Arizona; Museum of Northern Arizona; Desert Botanical 



