I MICROSCOPE AND AGRICULTURE 



under the microscope, its similarity to the more 

 simple fungus is evident. One of the gills also may 

 be carefully cut away and examined; the spores 

 will be seen at the end of small forked stalks. 



Having progressed thus far in our study of 

 fungus structure, we may examine a few of those 

 which cause damage in farm and garden. For the 

 most part, the thread-like portion of the fungus 

 grows within the plant attacked and only the spore 

 bearing portions appear on the surface. There is 

 one class of fungus, however, the Mildews in which 

 practically all the structure grows on the surface, 

 only a few small, unbranched suckers penetrate the 

 plant attacked, for the purpose of obtaining 

 nourishment. 



Though of great interest to the microscopist, the 

 potato disease is often the cause of serious loss to 

 the farmer. Not only potatoes but also tomatoes 

 are attacked. A potato plant suffering from the 

 disease has irregular yellowish or brownish spots 

 upon its leaves in the summertime. An examina- 

 tion of the lower surface of one of these spotted 

 leaves will reveal a silvery white margin to each 

 spot. This portion should be magnified with a fairly 

 high power and care must be taken not to injure 

 the diseased part of the leaf before it is examined. 

 In cases of serious disease, from nearly every 

 pore on the surface of the leaf fungus threads will 

 be seen to issue. The threads are branched and, at 

 the end of each branch, they have a special kind 

 of spore. They look not unlike miniature leafless 



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