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CHAPTER XII. 
SPORE-CULTURE., 
THE microscopic examination of the Uredinee and Usti- 
laginee is a very simple matter. The acidia 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 
zecidiospores 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 asufficiently 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, 
