FOREWORD 



On what has been left out. 



Most books begin with a preface explaining their 

 contents, and sometimes even apologizing for them. 

 To the present writer this seems an idle and unprofit- 

 able practice, for one can easily find out what is in 

 the text by reading it, and a book that requires an 

 apology had better be left unwritten. Sufficient ex- 

 planation for the bringing forth of this small volume 

 can be found in the pressing demand, hitherto unsat- 

 isfied, for a book in plain, non-technical English, on 

 the trees and flowers of the Yellowstone National 

 Park. It will be realized, of course, that where many 

 readers are to be reasonably well satisfied, few or none 

 can be satisfied with absolute completeness; certain 

 shortcomings are thus recognized as unavoidable and 

 therefore not to be apologized for. Time and space 

 will be more profitably employed considering the rea- 

 sons for omissions that seemed desirable or necessary. 



It is obviously impossible to include in a small 

 book a comprehensive treatment of all of the six or 

 seven hundred species of flowering plants to be found 

 in the Park. It is not even desirable, for many of 

 them are either rare, or inconspicuous, or obscure and 

 difficult of determination, and of interest only to pro- 

 fessional botanists. Some common-enough forms, like 

 the grasses and sedges, do not interest the average 

 visitor much, and moreover are determinable only by 

 experts. Others, finally, like the cattails, thistles and 

 wild mustards, are so familiar as to need no aid in 



