XX TREFACK. 



necessitating additional labour in transcribing, sorting, and 

 finally rejecting close upon three thousand duplicate titles. If 

 I had been able to arrange my titles under authors, instead of 

 subjects, many weeks' work in the aggregate would have been 

 spared me. As a key to the various subjects I would have an 

 ample index, not framed in the somewhat cumbrous fashion 

 adopted in both editions of Pritzel, but more in the manner of 

 Mr. B. R. Wheatley's Index to the Catalogue of the Library 

 of the Medical and Chirurgical Society. 



The arrangement I have adopted is that, which, after much 

 consideration, seemed best. I had to avoid increasing the 

 bulk of this volume unnecessarily, already more than twice 

 the size at first intended, and therefore shunned cross- 

 references as much as possible. Many books, treating of 

 several departments of botany, might fitly have gone in several 

 sections. In a few cases where I was unable to decide the 

 point, which subject was preponderant, I have given the book 

 in more than one section ; as an example, see Reinsch's Con- 

 tributiones in algologiam et fungologiam, on pages 156 and 164. 

 In using this volume, therefore, the reader must remember 

 that the grouping is a very rough one, and that he must refer 

 also to kindred subjects, if he would profit fully. As titles are 

 often insufficient and even misguiding, I may have placed some 

 books in sections different from those I might have chosen had 

 I been able to refer to the books themselves. Slight divisions 

 of subjects are usually marked-off by a rule. 



In each section the order is mainly chronological, but the 

 date of the last edition of each work is made to determine its 

 position in the roll ; this arrangement was adopted to enable 

 each author in question to adduce his latest views. I will not 

 trouble the reader with a somewhat complex code of regula- 



