Il6 BACTERIA IN RELATION TO PLANT DISEASES. 



where it is drawn, taking care, of course, in case of high magnification, to start one 

 cross line from the outside and the other from the inside of the image of the lines. 

 This method of recording magnifications is urged on all. It takes but a moment, 

 does away with troublesome computations, and enables anyone at any time to deter- 

 mine just what was the magnification. The magnification is determined, of course, 

 by dividing the apparent size by the actual portion of the scale shown. For 



Fig. 103* 



example, if the scale drawn on the paper is 10 mm. long and represents o.oi mm. 

 of the actual micrometer scale, then the magnification is X 1000; if it represents 

 the entire millimeter of the micrometer scale, the magnification is X 10. 

 For fine weighings, Christian Becker's balances are very satisfactory. 



*Fic. loj. Pillsbury slide-boxes empty and full, made by Bausch & Lomb, Rochester, N. Y. 

 These boxes are simple, inexpensive, and satisfactory, especially for serial sections. 



