viii PREFACE 



dead-looking, drab-colored neighbors ; or rearing their stately 

 heads far above the ordinary walks of life In columnar pillars 

 of towering strength. There is a fascination away out there 

 on the desert; nevertheless, unlike the strange weird mem- 

 bers of the cactus clan, we come not to stay, but only to enjoy 

 the charm of the desert, to study and learn, and then to 

 depart on our way. 



Without help from the following persons and organiza- 

 tions, It would have been Impossible for us to make such 

 careful study of these plants, so widely distributed over the 

 Southwestern deserts: 



We thank Dr. James Greenllef Brown and Dr. Hubert 

 Burley Streets of the University of Arizona for numerous 

 photographs; Professor Andrew Alexander NIchol of the 

 University of Arizona for rare species of cacti collected; 

 Dr. Forrest Shreve of the Carnegie Institution of Washing- 

 ton for specimens of plants and photographs; Evelyn Thorn- 

 ber for pen-and-ink drawings of cacti; Miss Frances Hamil- 

 ton, Mr. William Palmer Stockwell, Mr. Frank Henry 

 Parker, and Mr. Barnard Hendricks for assistance In making 

 careful studies of the cacti; the University of Arizona and 

 the Desert Botanical Laboratory of the Carnegie Institution 

 for help In procuring specimens of cacti for comparative 

 study. 



We are deeply Indebted to Mrs. John Wilmot Estill of 

 Los Angeles, California, for her exquisite paintings used 

 in this book. 



John James Thornber 

 Tucson, Arizona 

 Frances Bonker 



Pasadena, California 

 October 1, 1931 



