6 PREFACE. 



since here are important phenomena of considerable migrations being enacted 

 before our eyes. 



The issue of the presenl edition has been considerably hastened by reason 

 of the destruction of the supply of the first edition in the San Francisco 

 disaster of 1906. The student will find that the number of species has been 

 little increased over the first edition. It will also be aoted that many propo- 

 sitions of new species, especially of more recent years, do not here receive 

 mention, but it is by no means Implied that these are not of interest or of 

 value. It is only meant that the natural limits of time, endeavor and oppor- 

 tunity make it necessary and proper that results organized and available should 

 not be handicapped or unduly delayed by propositions which are the work 

 of many different hands and indicate many different points of view. Such 

 varied propositions should have that consideration which only a more prolonged 

 period affords. 



In the preparation of this edition the author is under obligation to not a 

 few botanists for suggestions, notes and specimens. Dr. H. M. Hall, Assistant 

 Professor of Botany in the University of California, has been helpful in many 

 ways and to him the author desires to express his obligations for many 

 courtesies. Many valuable notes, especially on the Liliaceae, have been received 

 from Mr. Carl Purdy of Ukiah. Mr. S. B. Parish has continued his kindly and 

 helpful aid. Dr. E. J. Smith has sent useful material from the Mt. Hamilton 

 Range. Revisions of the genera Trifolium and Nemoj>hila, respectively, have 

 been generously provided by my former students, Miss Laura F. McDermott 

 and Mr. Harley P. Chandler. The account of the grasses by Mr. J. B. Davy, 

 now Botanist to the Transvaal Government, has been reprinted substantially 

 without change. Miss Leila D. Hibbard, one of my students, contributed wel- 

 come aid in the arrangement of the manuscript for the printer. Many others 

 who have furnished notes or specimens find mention at proper places in the text. 

 Finally acknowledgment is due to Mr. Joseph W. Flinn, University Printer, 

 for his expert advice in regard to matters connected with the printers' art. 



Willis Linn Jepson. 

 1 department of Botany, 

 University of California, Berkeley, 

 February 2, 1910. 



