FUNGI. 19 



fungi known to cause diseases of economic plants. Again, our 

 fathers were neither as observant nor as provident against loss as 

 their experience has taught us to be, in certain directions. Crops 

 were damaged or destroyed by blight or mildew, and their owners 

 merely accepted the fact with philosophic resignation, laying the 

 blame upon the weather, or some mysterious agency unintelligible 

 to man and against which there could be no protection. Today 

 we are not content with such conclusions. "We subject the soil to 

 chemical analysis to ascertain what element of plant-food it lacks, 

 and that element we supply artificially. We examine the plants 

 themselves microscopically, knowing that there are parasitic 

 plants, practically invisible to the naked eye, but capable of 

 doing immense damage under favorable conditions of temperature 

 and moisture. 



Still again, many parasitic fungi which cause a diseased condi- 

 tion of cultivated plants, are found to have originated on wild 

 species related to the cultivated. So long as the fungus limited its 

 depredations to the wild plants it was considered of no economic 

 importance. As soon, however, as it transferred its attentions to 

 the related cultivated plant, its effects became an object of concern, 

 and that particular economic plant was said to be subject to a new 

 fungous disease. Familiar examples of this are seen in the case 

 of the "black-knot" of the wild cherry and plum, which when 

 transferred to cultivated varieties becomes an object of dread to 

 the fruit grower; and the common orange "rust" of the wild 

 blackberry, which upon the cultivated varieties becomes a well- 

 nigh ineradicable disease. 



Finally, it is more than possible that the increase of fungous 

 disease may be due to our methods of hybridization and so-called 

 improvement of stock. Just as an athlete may become over- 

 trained to the point of collapse, in case his training is directed 

 toward the special development of only one manifestation of 

 vigor, so is it possible to cultivate and concentrate the energy of a 

 certain vegetable stock to such a degree in one direction, that it is 

 vitally weakened in other more essential particulars, and made 

 peculiarly susceptible to adverse circumstances, whether of 

 climate, soil, or parasitic disease. This fact is slowly finding 

 recognition in the case of apples, where pomologists are more and 

 more turning their attention to the production of hardy and 

 resistant varieties, rather than varieties which are remarkable for 

 fruitage alone. 



