52 THE POTATO CROP. 



as one of the healthiest of our " Farm Crops," the injuries, 

 though noticeable more or less in different districts every 

 year, being too slight to influence practically its produce 

 in the field. In 1845, however, this idea of its natural 

 health and freedom from injury was dispelled by the 

 appearance of a disease of a peculiar character, differing 

 materially from those previously known, and which spread 

 itself far and wide over the country, leaving scarcely a 

 single field without sad evidences of its visitation. From 

 the virulence and prevalence of this attack, it was regarded 

 as a murrain, and received the name of "the potato dis- 

 ease/' by which it is best known even at the present time. 

 The effect of this disease is too well known, and its 

 cause too little known notwithstanding the investiga- 

 tions of scientific, and the opinions of practical men to 

 justify any lengthened remarks here: all we shall attempt 

 will be to sum up the results of these investigations and 

 speculations) and see how far any deductions may be 

 drawn from them that may be made practically available 

 in the field. Before we attempt this it will be well to 

 give a passing notice of the other forms of disease, such as 

 "the curl," "the scab," and "the dry rot," to which the 

 potato crop has been for a long time past more or less sub- 

 ject. The "curl" is a diseased condition of the stem, first 

 exhibited in the leaves, which, though in appearance green 

 and juicy in their centres, become curled and twisted at 

 their edges. This is more frequently met with in some 

 varieties than in others ; and it is also more prevalent in the 

 northern than in the southern parts of the country. Martius, 

 in his treatise on the "Diseases of the Potato," thus describes 

 it: "The curl is an imperfect formation. Soon after 

 their first appearance the shoots become curled, and make 

 but little progress afterwards; sometimes, indeed, they 

 disappear altogether. Some, however, remain nearly sta- 

 tionary either not producing blossoms at all, or only 



