MILDEWS. 51 



remaining so. Just as a sound, vigorous, well-fed man will expose 

 himself where any other, weakened in any respect, would contract 

 disease at once, so a plant with well-developed organs of assimila- 

 tion and supplied with an abundance of the crude material of food 

 will often resist the attacks of parasites, or will have no trouble in 

 providing sufficient food for itself and for them beside. In this 

 lack of rational feeding, in respect to both quality and quantity, 

 lies, I believe, the secret of much disease and susceptibility to 

 disease in both animals and plants. 



Discussion. 



Benjamin P. "Ware believed that if the germs of potato rot are 

 retained in the tubers by their vegetative threads, they have power 

 to develop only under favorable conditions, and might in time be 

 destroyed did not such favorable conditions appear. He con- 

 sidered it hardly safe to say we do not have any, for he believed 

 there would always be enough preserved to keep the fungus along. 

 Under favorable conditions the disease would spread over a whole 

 field in from thirty-six to forty-eight hours. 



Professor Humphrey replied to remarks and questions : The 

 spreading of potato rot ensues after the fungus has "struck." 

 Many experiments have been tried to find a remedy that may be 

 applied at planting time, but thus far without success. When 

 there is infection of the tuber to an}- extent, there is usuall}' dis- 

 coloration, but it may be too slight to be readily perceived. For 

 study with the microscope, the potato must be cut in thin slices, 

 which destroj^s it for planting. 



Winter spores of the lettuce mildew are not produced under 

 glass. But the existence of summer spores may thus be prolonged. 

 Dryness in the summer may destroy the spores. Undoubtedly 

 spores may be produced in leaves that are thrown away. "Winter 

 spores may thus be developed. "We cannot yet wholly clear up 

 this matter. 



"William D. Philbrick said he had noticed that whitish spots 

 appeared in muggy weather in August upon both sides of the 

 leaves of violets growing out of doors. The spots were white at 

 first, then grew darker, and the leaf dried up. He had found the 

 disease most troublesome in the fall. Sometimes the violet plants 

 are all killed out. If any survive until Christmas they will revive 

 in the spring. 



