POTATO- ROT. 215 



that plant, but it also infested the common sow-thistle, chiccory and 

 some other plants, and in the tissues of these last were formed the 

 resting spores which were able to continue the existence of the 

 parasite through the cold winter months, when it again attacked the 

 lettuce. Other species of Peronospora are confined to a single host 

 plant. From all this knowledge of other species, botanists were 

 quite in doubt where or when to look for the resting spores of 

 Peronospora infestans, Alont. The leaves and tubers of diseased 

 plants were examined again and again without success, and the sus- 

 picion began to prevail that clover might be the plant within which 

 the resting spores were formed, and man3- farmers were inclined to 

 regard the clover plant with suspicion thinking that it might in some 

 way be favorable to the potato disease, and even the stable manure 

 from animals fed on clover hay was not used under potatoes. It 

 was thought by some, and not without good reason, that the resting 

 spores were not only able to retain their vitality in the tissues of the 

 clover during the cold of winter but also in their passage through 

 the alimentary canal of the animals fed on the clover. Experiments 

 in planting potatoes on newlj' plowed clover lands, and also on 

 manure from clover fed animals as often gave negative results as 

 anything else, so that the farmers were totally in the dark, not know- 

 ing what to do, as often doing the verj' worst thing as the best, till 

 at last it was impatiently asked " wh}' don't the scientists do some- 

 thing for us?" The problem which they had asked to have solved 

 was one of the most intricate and difficult which had ever been 

 undertaken by the botanists. Not only was the most profound 

 knowledge of the related fungi required, but also the most con- 

 summate skill in the use of the microscope and its accessories. The 

 7nost extreme care is required in any attempt to cultivate these 

 minute objects, a mere trifle too much of moisture may destro}^ them 

 or the merest breath of air which is too dry ma}'' cause the whole 

 colony to collapse, and the labor of weeks be lost. Furthermore, 

 the scientists were expected to do this work gratuitously. I am not 

 aware that a single dollar was ever given by any government, state 

 or society to aid in the investigations on the potato fungus with one 

 single exception. The Royal Agricultural Societj' of England 

 appropriated $500 to aid De Bary in his investigations on this plant. 

 In the early part of June 1875 the editors of the London Journal 

 of Horticulture called the attention of Mr. W. G. Smith, one of 

 the foremost cryptogramic botanists in England, to what was then 



