MICHIGAN ACADEMY OF SCIENCE. 289 



the lower leaves. The air in the bell jars was kept saturated during the 

 entire experiment. The plants were placed side by side in the green- 

 house. Thus all conditions were equal except that the lower leaves of 

 the half darkened plants received only what light filtered through the 

 upper leaves, whereas the other two plants received light from the sides 

 as well. After eleven days a comparison between the two sets of plants 

 showed that the lower leaves of the half darkened plants, besides being 

 partially etiolated, bore more and larger spots than the lower leaves of 

 the fully lighted plants. Twenty leaflets of the former picked at ran- 

 dom, bore fifty-one spots compared with thirty-seven spots on a like 

 number of the latter. 



In the case of plants kept in total darkness, the fungus was found 

 to infect and spread very rapidly. The spots besides being large caused 

 the death of considerable tissue beyond them. Although darkness has 

 not been found to affect the growth of the fungus itself, it may be that 

 the clover plant, either because of a weakened condition or an increase 

 in succulence has become more susceptible. 



INOCULATIONS UPON OTHER HOSTS. 



Alsike Clover: 



Bain and Essary, (1905), stated that M. sarcinaeforme was often found 

 upon stray alsike plants associated with red clover in Tennessee. Re- 

 peated attempts were made to infect alsike clover, but without success ; 



The following experiment which has been repeated several times 

 during this study is typical: A pot of red clover and a pot of alsike 

 clover plants in about the same stage of development were sprayed 

 thoroughly with a susjaension of spores, and both pots kept under the 

 same bell jar. .Within the usual time the red clover plants were infected, 

 but never the alsike. None of the other methods of inoculating, even 

 using a heavy inoculum, produced infection, and no noticeable effect 

 aside for an occasional slight discoloration of the leaf, lias been ob- 

 served. Wounded leaves also failed to take the disease. Other inocula- 

 tions were made upon young seedlings and plants in various stages of 

 growth, without success. In the field, completely healthy alsike plants 

 have often been observed growing in the midst of badly diseased red 

 clover. 



We may conclude that the strains of alsike clover tested under East 

 Lansing conditions are not susceptible to the strain of M. sarcinaeforme 

 found upon the red clover growing in this vicinity. Unless we postulate 

 marked differences in disease resistance in strains of alsike clover, these 

 results seem to indicate that the statement of Bain and Essary (1905) 

 ascribing the leaf spots of alsike and red clover to the same organism is 

 incorrect. 



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