302 Agricultural Experiment Station, Ithaca, N. Y. 



subject to the disease. This, however, is not necessarily due to 

 the foliage of such A^arieties being more susceptible, but rather 

 to the habits of the fungus. I have not observed that the age 

 of the potato plants has a marked influence upon the spread of 

 the disease; nor that the young foliage of the plants is less 

 subject to the disease. It appears as if the parasite is able to 

 thrive upon all potato foliage which is in a healthy condition at 

 the time of the germination of the spores, and that old and young 

 foliage or plants suffer practically to an equal extent. This mat- 

 ter is here emphasized because it will be considered again in con- 

 nection with the early blight of potatoes. 



2. Early blight; Leaf-blight {Macrosporium Solani, E. & 

 M.). — It is only within the past five or six years that the early 

 blight of potatoes has been recognized by scientists and farmers 

 as a distinct disease.* The trouble has been known during a 

 longer period, and its general character fairly well understood. 

 But the attention which in former years was given to the potato 

 rot fungus caused this second disease to be overlooked, or at least 

 to be regarded as perhaps a peculiar condition resulting from the 

 attacks of late blight, or from certain conditions unfavorable to 

 the growth of the potato plant. But since 1891 the fact has been 

 clearly established that two distinct evils have preyed upon potato 

 foliage, and since that time the second trouble, or, as it has been 

 popularly called, the " early blight," has received considerable 

 study. 



The one character which was probably the most valuable in 

 distinguishing the two diseases is the fact that plants having the 

 early blight do not necessarily have rotten tubers, but on the con- 

 trary these are almost invariably perfectly sound, although small. 

 The slow progress of the disease, and the peculiar discoloration 

 and shriveling of the plants also made it apparent that there were 

 two distinct diseases affecting the crop. 



But the real cause of this trouble has not been found with equal 

 readiness and certainty as was the case with the potato rot. Al- 

 though at first it appeared as if the entire trouble could be laid at 



*For bibliographies of the enrlier contributions conceraing the early blight 

 of potatoes, see Jones, 6th Ann. Kept. Vt. Ajjric. Exp. Sta. 1892, 66 et .seq. Also 

 Stiiryie, 18th Ann. Kept. Conn. Agric. Exp. Sta. 1894, 127 et beq. 



