MICHIGAN ACADEMY OF SCIENCE. 



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Method 1 — The plants are first drenched with water (sprinkling pot) 

 and then sprayed with a suspension of spores in sterile water. The 

 plants are then kept in a humid atmosphere under a bell jar. It was 

 found that the droplets containing the spores adhere much better if the 

 leaves are first drenched with water. By this method, characteristic 

 spots develop within five to seven days. 



Method 2 — Small masses of fungus growth (spores and mycelium) are 

 placed upon the upper surface of the leaflets, the inoculum covered with 

 a tuft of cotton, and the plants kept under a bell jar as above. 



Method 3 — A drop of spore suspension is carefully placed upon the 

 leaflets by means of a capillary pipette and then covered with a tuft of 

 cotton. This retains the moisture and prevents the droplet from rolling 

 off the leaf. The plants are kept under a bell jar. 



Inoculations made by either of the last two methods do not give typical 

 spots. The leaf tissue surrounding the inoculum was progressively killed 

 within twelve to fifteen days. 



During tliis study red clover plants were inoculated many times under 

 a variet)' of conditions, using all the methods above described. Successful 

 infection was almost invariably secured. (The failure to secure inocula- 

 tions after long cultivation of the fungus will be discussed later.) 



Infection experiments with young and old leaves: » 



The following experiment was undertaken to determine the relative 

 susceptibility of red clover plants in the various stages of their develop- 

 ment: 



Table 2. 



Infection of Plants in Various Stages of Development: Test with Potted 



Plants under Bell Jars. 



