BOTANICAL BOOKS AND THEIR USE 127 



most readable and illuminating, though one now much 

 behind the present state of knowledge, is Sachs's " Lec- 

 tures on the Physiology of Plants," a work that should 

 be much used for the value of its point of view. The 

 greatest work on physiology is Pfeffer's "Pflanzen physi- 

 ologic," of which Volume I has appeared, with Volume 

 II to follow soon; the work is being translated into 

 English, and will be indispensable to every botanical 

 library. Another most excellent book, very direct and 

 suggestive, is Sorauer's work, translated by Weiss as 

 " Popular Treatise on the Physiology of Plants." Vines's 

 " Lectures on the Physiology of Plants ' is also very 

 excellent, though now needing revision. A book much 

 used in this country is Goodale's "Vegetable Physiol- 

 ogy," a clear synopsis of its subject, but now also much 

 in need of revision. Of course the various modern 

 text-books to be mentioned later contain physiological 

 sections. 



The very important and rapidly developing subject 

 of ecology has not yet many good works in English. 

 First among them are several of Darwin's books, which 

 are foundation works in some phases of ecology. 

 Highest among general works would stand Kerner and 

 Oliver's " Natural History of Plants," which is to be 

 consulted with the caution already referred to. In 

 German there are important works by Ludwig and by 

 Wiesner. In one of its most practical and interesting 

 aspects, namely, in the explanation of the causes of 



