1 68 FUNGOUS DISEASES OF PLANTS 



attention of scientists. The early work was remarkable for its 

 time, but the actual results accomplished lose their value now 

 on account of the fact that the older varieties have largely dis- 

 appeared from cultivation. Excellent work was done during the 

 early part of 1 8 70- 1880, when Charles Darwin himself became 

 much interested in resistance breeding, 187 2- 1878. As a result 

 of the interest which was then established, the various wild 

 species of potato growing in South America were carefully studied 

 with reference to this point and numerous crosses and selections 

 made. Again, during the past ten years there has been a re- 

 vival of interest in this subject, and to-day the general problem 

 is better understood and the results will probably be more lasting. 

 It may be said, however, that while many varieties have been de- 

 veloped which show a considerable degree of resistance, yet it is 

 also true that no variety may be expected to maintain such resist- 

 ance throughout a long period of time. Gradually there will be 

 deviation from the original sort, and, moreover, its relation to the 

 particular environments in which grown will doubtless also affect 

 the relations to the blight organism. 



It cannot be expected that a single variety will be equally re- 

 sistant under different conditions. Therefore, in diverse localities 

 and particularly in different regions variations will be apparent. 

 The studies which have thus far been made upon resistance have 

 concerned both foliage and tuber resistance. According to the 

 experiments in Vermont (Stuart) Rust Proof was most resistant 

 in 1903, so far as the foliage is concerned, and the Dakota Red 

 was second ; while in 1904 the order was as follows : Monterey, 

 Solatium Commersonii, Solatium polyadcnium, Rust Proof, Sut- 

 ton's Discovery, June, Mexican, Mammoth Gem, and Manum's 

 No. 3. With relation to tuber resistance Dakota Red has made 

 the best showing for two seasons, although it was not wholly free 

 from rot. The other varieties which show least blighting of the 

 foliage were also resistant to the rot. The following interesting 

 summary has been drawn : 



1. Some varieties are less subject to vine injury than others. 



2. Some show a greater tuber resistance to rot than others. 



3. With some there seems to be a fairly close relation between 

 resistance of vine to disease and of the tuber to rot. 



