THE POTATO. 147 



tatoes ; but it is of great service to c the breeder,' 

 who seeks to improve its quality. No vegetable is 

 more yielding to the hand of the cultivator than 

 this plant. Raising it from seed enables him to 

 obtain varieties without end, and attention to the 

 qualities of those between which the crossings take 

 place, admits of obtaining any particular quality that 

 may be wanted. 



On the other hand, by cultivation from the tubers 

 a good variety may be extended and preserved after 

 it has been once obtained ; as the plant from the 

 tuber is not a new plant, like that which is procured 

 by the operations of flowering and seeding, but an 

 identical part of the old one. Though the planting 

 tubers will not lead to any new variety, it may have 

 effects every way as advantageous ; for no plant 

 profits more by changes from one district to another. 



Besides improvement in quality which a judi- 

 cious change produces, it likewise often prevents the 

 most destructive disease to which the potato is 

 liable. That disease is known by the technical 

 name of the curl or the curl-top, a name by no means 

 inexpressive of the appearance of the plant, when 

 under its influence. The top leaves begin to shrink 

 just about the time that the tubers should form, the 

 young shoots cease to expand, and the whole plant 

 assumes very much the appearance of the tip of a 

 cherry twig, when the under leaves are assailed by 

 aphides. From the moment in which this disease 

 appears, all farther growth in the plant ceases, and 

 though it may linger in a yellow and sickly state 

 until autumn, the produce, if any, is little, and that 

 little is of a bad quality. If, as soon as the disease 

 shows itself, the tuber which has been planted be 

 taken up, it will be found much firmer and less ex- 

 hausted than those of the plants of the same age 

 that are in a healthy state. This at the same time 

 points out the cause of the disease, and suggests 



