^jy^^^^^/^^/^';^zu^^ 97^-^^ c-''U^<^-te^. 





[Reprinted from Studies in the Biological Sciences, No. 4.] 



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 ^'"'-'^ .v-;:k: 



ARTHUR MONRAD JOHNSON 



IN PARTIAL FULFILLMENT OF THE REQUIREMENTS 



FOR THE DEGREE OF 



DOCTOR OF PHILOSOPHY 



JUNE 1919 



