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CHAPTER XII. 



SPORE-CULTURE. 



The microscopic examination of the Uredineae and Usti- 

 lagineae is a very simple matter. The secidia viewed as 

 opaque objects with a low power are always very attractive 

 objects. To examine the various spore-forms, all that is 

 necessary is to remove a small quantity with the point of 

 a penknife, place them in a drop of water on a glass slide, 

 and, having covered them with a circle of thin glass, view 

 the preparation as a transparent object with a quarter-inch 

 objective. The various markings on the exterior of the 

 aecidiospores and uredospores are more readily seen if they 

 be examined dry. In order to obtain more accurate in- 

 formation of the structure of the spore-beds, thin sections 

 must be cut with a sharp knife, including both the spore- 

 bed and a small portion of the host-plant. With a little 

 patience, and by teazing out the cells of the host-plant, the 

 mycelium can be observed. This is often rendered more 

 conspicuous by the application of a drop of caustic potash. 

 To observe the germination of the spores is not difficult, 

 and can be accomplished without the aid of expensive or 

 elaborate apparatus. All that is necessary is to place the 

 spores in a sufficiently humid atmosphere, or in a sufficiently 

 moist place. This may be conveniently accomplished by 

 placing a drop of pure water upon an ordinary glass slide, 



