68 MINNESOTA STUDIES IN PLANT SCIENCE 



Canadian Rocky Mountains ; to Dr. William S. Cooper for helpful suggestions touch- 

 ing ecological factors ; to Dr. Oscar W. Oestlund for many inspiring ideas and guiding 

 principles drawn from his fund of knowledge of the science and philosophy of tax- 

 onomy. Especial thanks are due to Dr. W. R. Maxon, of the United States National 

 Herbarium, for the loan of indispensable herbarium material; likewise to Dr. George 

 T. Moore and Dr. J. M. Greenman for the loan of a large collection from the Her- 

 barium of the Missouri Botanical Garden. The writer wishes also to express his 

 thanks to Dr. H. M. Hall for specimens from the Herbarium of the University of 

 California ; to Mr. F. S. Hall for specimens from the Herbarium of the State Museum, 

 University of Washington, Seattle ; to Dr. F. L, Pickett, Washington State College, 

 Pullman, Washington, for specimens from that region ; to Dr. J. E. Kirkwood, Uni- 

 versity of Montana, Missoula, Montana, for specimens from the Rocky Mountain 

 region ; and to Mr. Alonzo P. Troth, of the Lewis and Clark High School, Spokane, 

 Washington, for fresh material from the Spokane Valley. 



Owing to conditions resulting from the World War Engler's monograph on 

 Saxifraga in Das Pfiansenreich (IV:117:I. 1916, IV:117:II. 1919) was not obtain- 

 able when this paper was in process of preparation. — Author. 



Universitv of Minnesota, 1919. 



