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affected whenever the spores come in contact with the plant 

 under conditions of liigli temperature and moisture. These 

 spores are produced in immense numbers, an illustration 

 of which may he seen in mass of spores forming the large 

 fruit-hunches of the " corn-smut " or the dust of the puff- 

 ball, the hlack substance of the first and the fine gray 

 powder of the last being composed of myriads of spores or 

 seeds. These spores are very small, so small in fact that 

 they are individually scarcely perceptible to ordinary vision 

 and are carried about by the slightest breath of air. 



Much may be done to prevent the growth of fungous 

 pests by keeping the trees or plants in a vigorous, healthy 

 growth. This may be done by good cultivation and an 

 abundance of plant-food, under which condition the grow- 

 ing spores are not so likely to gain a foothold in the tissues 

 of the host plant; but even with the most vigorous growth 

 we sometimes find that if the weather is unusually hot and 

 the atmosphere very moist the spores will gain a foothold 

 and we must have the copper solutions on the surface of 

 the plant to prevent the growth of the spores should the 

 plant not be able to withstand their attack. 



Some seasons, and often for a series of years, our trees 

 escape injury from fungous pests, but we cannot hope to 

 escape always, and it is the part of wisdom to learn with 

 what pests we are threatened, what is the best remedy, and 

 how and when to apply such remedies as to most certainly 

 destroy each pest. 



Fungicides. 

 (Fungus-destroyers.) 



COPPER SULPHATE (Blue Vitriol). Copper has long been 

 known to be destructive to the spores of nearly all kinds of 



