WINTER MEETING. 203 



ried about by birds, animals and insects, and are finally lodged on 

 healthy plants, where they germinate. In germinating they send their 

 thread-like mycelium into the healthy plant, suck up its juices, destroy 

 its tissues, and eventually produce fruiting parts ( similar to toadstools 

 or puft-balls, only very much smaller), on the leaves or fruit, which shed 

 their spores as described. Some of these fungi produce spores that 

 are too small to be seen by the naked eye. In such cases we only see 

 the clusters of fruiting-heads, or the decaying and shriveled parts of 

 the host plant, where the spores are breaking out. The little black 

 dots that occur in blotches called apple " scab," and the concentric 

 rings of dots on the bitter rot of apples, are each a spot where a fruit- 

 ing-head of the fungus is breaking through the skin of the apple, and 

 pouring out a quantity of tiny spores. 



It is sometimes asserted that these diseases of fruits are caused by 

 the weather instead of by fungi. This statement is similar to sajing 

 that weeds are caused by hot weather instead of growing from seeds 

 which are scattered through the soil. It is true, that these fungi grow 

 best when conditions of weather are favorable. Most of the rots, 

 scabs, rusts, etc., develop most rapidly during moist, hot weather. The 

 grayish fungus which causes root-rot of young apple-trees develops 

 best in a cool, wet soil. Mushrooms spring up most plentifully when 

 cool, wet nights follow a long hot spell. In all these cases, however? 

 the fungus grew from spores and only waited for favorable conditions 

 to develop other spores, just as weeds grow from seeds when the 

 weather is warm, and develop other seeds. Just as weeds grow, only 

 when weed seed is present, so do these diseases of our fruit develop, 

 only when these fungi are present. 



Since these fungus diseases propagate by means of spores, the 

 key-note to the spraying operation is to spray the plants with a mixture 

 that will kill these spores, as they lodge on the plant ready to germi- 

 nate. In order to do this successfully, however, we must understand 

 the entire life history of the individual fungus we wish to fight. It is 

 not enough to simply apply a spray a few times during the growing 

 season of a plant and conclude that it is sufiQcient to cure all its ills or 

 kill all the fungus diseases with which the plant may be etTected. We 

 should know at just what season each fungus ripens its spores, when 

 and where these spores are most liable to germinate, whether the fungus 

 lives over winter in the mycelium stage, and a host of other complica- 

 tions that may arise. 



Since this paper is written mainly to emphasize the need of a bet- 

 ter understanding of the fungi, rather than to give the formulas and 

 rules for spraying that are so frequently published and so easily acces- 



