54 THE POTATO CROP. 



very closely compacted, and at length burst forth in the 

 form of little white cushion-shaped tufts, loaded with fruc- 

 tification. Not only were the tissues themselves attacked, 

 but even the starch granules were often covered with vege- 

 tation. The entire tuber became sometimes so hard as to 

 make it difficult to break it even with repeated blows of a 

 hammer/' This form of disease exhibited itself some years 

 before the "potato disease" was known. The "dry rot" 

 was constantly accompanied by Fusisporium solani,' to 

 the presence of which Martius attributes the disease. 



The "scab" affects the stem and the leaves, producing 

 patches of a brown colour, which become larger as the 

 disease progresses, and thus exert a greater influence upon 

 the health and vigorous development of the plant. This 

 form of disease, which exhibits itself on the tubers, and 

 lessens their value, however, is less injurious in its effects 

 than the curl ; and both, indeed, have of late years been 

 well-nigh forgotten in the presence of the more serious 

 injuries inflicted on our crops by the " potato disease." Pro- 

 bably no subject affecting inanimate nature has attracted 

 such general attention to it by scientific as well as practical 

 men all over Europe as this peculiar disease ; and yet, not- 

 withstanding all their researches, we know but very little 

 more about it, or rather its cause, than we did at the time 

 it first made its appearance in our fields. Its effects, how- 

 ever, have been more satisfactorily observed ; and far less 

 difference of opinion exists on that head than still exists 

 as to the part of the plant on which the disease first mani- 

 fests itself. Even now, if the question be asked, some will 

 reply that the leaves are first affected, some that the stem 

 exhibits the well-known patches of decay, while others, 

 again, trace its source to the "set" or seed -tuber itself, 

 whence it ascends to both the stem and the leaves. The 

 general opinion of those qualified to give one, appears to be 

 that the disease first exhibits itself in the stem and leaves, 



