MICROSCOPE AND AGRICULTURE 



trees and they give the typical silvery white appear- 

 ance to the margins of the diseased spots. When 

 the spores of potato disease germinate, the young 

 fungus threads enter the leaf through a pore and 

 for sometime afterwards there is no sign that the 

 plant is diseased. On this account potato disease 

 and may other fungus diseases are rendered more 

 serious in that the farmer is not and cannot be 

 aware that his crop is attacked till the disease has 

 taken a firm hold. Eventually the potatoes them- 

 selves become brown, rotten and breeding grounds 

 for bacteria. 



A very common plant disease which makes a good 

 study for the microscope, may be found in quantity 

 upon shepherd's purse, and as it also attacks culti- 

 vated plants of the same family, cabbages, cauli- 

 flowers and the like, it is of no little importance. 

 In its early stages, the fungus looks like patches 

 of thick white paint upon the plant and where the 

 fungus grows the plant is invariably contorted. As 

 the fungus matures, the skin of the diseased plant 

 splits and a white powder issues. If some of this 

 powder be highly magnified, it will be found to 

 consist of chains of spores, six or seven in a chain. 

 The spores break off singly and each one may start 

 the disease in another plant. 



The microscopist who hunts in garden and farm 

 for fungus diseases, will assuredly meet with some 

 examples of that large class known as " smuts." 

 They are so called on account of the black powder 

 with which the attacked portions of the plants 



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