162 DISEASES OF CROPS. 



Canada balsam or glycerine. If opaque, ttey should be 

 mounted in Canada balsam. Both, animal parasites and 

 sections of infested plants can be mounted in water or 

 dilute glycerine when not required as permanent objects. 

 If, on the other hand, sections of infested plants are to be 

 permanently mounted, the best preservative media are 

 glycerine jelly and Canada balsam. 



Concerning the methods of using the microscope, section 

 cutting, hardening, staining, and mounting objects, the 

 author refers his readers to the undermentioned books i^— 



Carpenter's The Microscope and its Revelations. 



Trey's Mikroskop und die Mikroskop Tecknik. 



Beale's How to Work with the Microscope. 



Griffiths and Henfrey's Micrographic Dictionary. 



Hogg's The Microscope, etc. 



Martin's Manual of Microscopic Mounting. 



Marsh's Section Cutting. Davies's Practical Microscopy. 



Naegeli and Schwendener's The Microscope in Theory 

 and Practice. 



Duval and Lereboullet's Manuel du Microscope. 



The scope and object of the present work necessarily 

 prevent the author from writing at length upon the above 

 subjects ; but it may be mentioned that a good pocket 

 magnifier is indispensable for the working economic bio- 

 logist. In conclusion, "the microscope is an instrument 

 imperative to all who would cultivate their minds by the 

 possession of a store of interesting facts and rank well as 

 intelligent beings in society." In economic biology, or 

 the biology of the farm, it is indispensable as an auxiliary 

 to the scientific inquirer into the causes and effects of the 

 diseases of farm crops. 



