258 Wisconsin State Horticultural Societt. 



used, may enable the general reader to get a better understanding 

 of the whole subject. 



The views herein stated, and the conclusions presented, are 

 mainly compiled from the opinions and observations of Professors 

 Cooke, Berkeley, Taylor, Smith, Farlow, De Barry and others. 

 Perhaps no one of the authorities named would be willing to as- 

 sent to the complete statement as made, or accept entirely the 

 deductions drawn, for there is much diversity in their individual 

 opinions on some of the points presented, but the conclusions 

 presented are those to which a limited personal observation and 

 a careful study of the different views and observations given by 

 these investigators seem most naturally and conclusively to lead. 



Various theories have from time to time been advanced as to 

 the primary cause of this disease. Many of these theories have 

 been proved to be fallacious, but there are two still held, both of 

 which have earnest adherents. One is, that it is the result of a 

 general loss of vitality, a deterioration of the plant itself, brought 

 about by unfavorable conditions of soil or climate, or both ; the 

 other is, that it i3 primarily, wholly caused by fungoid or para- 

 sitic growth. All agree that fungus is found in connection with 

 the disease and, that in certain conditions, it is an active agent in 

 hastening decay. Those who hold the opinion first stated claim 

 that this fungus growth comes as the result of, and is only made 

 possible by, a previous unhealthy, diseased condition of the plant, 

 and that it is a natural provision for the reduction of decaying 

 organic matter to its original elements. The others say that it 

 can lay hold of healthy tissue and unaided destroy the vitality of 

 the plant. With one or two exceptions, those who have investi- 

 gated the subject the most thoroughly favor the first theory or 

 express strong doubts as to the correctness of the last, but the 

 exceptions noted are very positive in the assertion of the truth of 

 their position. Facts, clear, unquestioned facts alone can demon- 

 strate which view is correct, and those investigating the subject 

 must, each for himself, draw such conclusions as the facts at com- 

 mand seem to warrant, or hold the matter in abeyance until we 

 have more light. 



The fungus found in connection with the potato rot is called 



