Flowering Plants and Ferns of Arizona 



By Thomas H. Kearney, 'principal physiologist, and Robert H. Peebles, 

 associate agronomist, Division of Cotton and Other Fiber Crops and Diseases, 

 Bureau of Plant Industry, and collaborators 



CONTENTS 



Page 



Introduction 1 



Collaborators 2 



Plan of the work 3 



Economic information 5 



Botanical exploration of Arizona. 5 



Geographical relationships of the flora 7 



The vegetation of Arizona 10 



Types of vegetation 12 



Vegetation of the Grand Canyon 23 



Page 

 Annotated list of the plants of Arizona, with 



keys - 24 



Pteridophyta 24 



Spermatophyta 45 



Addenda 1034 



Literature consulted 1036 



Vegetation of Arizona^ 1036 



Uses and popular interest .. ,' 1037 



Index 1041 



INTRODUCTION 



Arizona ranks very high among the States in the richness and diver- 

 sity of its flora. Approximately 3,200 species of flowering plants and 

 ferns, growing without cultivation, are known to occur within its 

 limits. Many other species have been collected so near the borders 

 of Arizona that they are almost certain to be found in the State. Fur- 

 thermore, much of the area has not yet been explored thoroughly, so 

 it is highly probable that the Arizona flora will be found, eventually, 

 to comprise not fewer than 3,500 species of higher plants, even with 

 the conservative conception of what constitutes specific rank that the 

 authors have sought to maintain. 



The number of families of flowering plants represented in this flora 

 is 121 , in addition to 7 families of ferns and fern allies. The 10 fami- 

 lies comprising the largest number of species are as follows: 



_, Number of 



ramily. species 



Compositae '518 



Gramineae 325 



Leguminosae 2S3 



Scroph nlariaceae 108 



Cruciferae 97 



_, Number of 



Family: species 



Polygonaceae 91 



Cyperaceae 89 



Euphorbiaceae 80 



Cactaceae _ 76 



Rosaceae 66 



The leading families, it will be noted, are mainly those occupying 

 this rank in other North American local floras and, to a large extent , in 

 all temperate parts of the Northern Hemisphere. The outstanding ex- 

 ception is the family Cactaceae. No other State of the Union, save 

 Texas, has so rich a representation of this group, and 1 1 of the 76 

 species occurring in Arizona have not been found hitherto beyond its 

 borders. 



It is surprising that there has never been a comprehensive publica- 

 tion dealing with this extraordinarily interesting State flora. In the 



