MICHIGAN ACADEMY OF SCIENCE. 73 



Artificial inoculation is comparatively easy to carry out in the laboratory. 

 Sori develop in six to ten days after inoculation with sporidia. Cool weather 

 seems to be favorable to the development of this fungus. 



In the portions of the tissue where the mycelium works, be it leaf, stem or 

 petiole, it develops mainly between the cells which Ijecome pushed apart so 

 that the distance from one cell cavity to another is about as great as the 

 diameter of the cell (figure K). Once in a while an haustorium may be seen 

 (figure H), but the mycelium is intercellular. 



Agricultural College, Mich. 

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