A REVISION OF THE NORTH AMERICAN SPECIES 



OF THE SECTION BORAPHILA ENGLER 



OF THE GENUS SAXIFRAGA 



(TOURN) L. 



A THESIS 



SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL 



OF THE UNIVERSITY OF MINNESOTA 



BY 

 ARTHUR MONRAD JOHNSON 



IN PARTIAL FULFILLMENT OF THE REQUIREMENTS 



FOR THE DEGREE OF 



DOCTOR OF PHILOSOPHY 



JUNE 1919 



