THE POTATOE DISEASE. 123 



tubers, and Mr. Thompson tells me, that when the haulm 

 was pulled up at the Horticultural Society's Gardens, the 

 crop of tubers was less and the disease was worse. This 

 plan is not, however, to be adopted for the benefit of the 

 plant itself, but only for the purpose of destroying vast 

 nations of the Aphides. 



(481.) Every wise farmer would isolate the crops which 

 are liable to be affected by the malady. He would not 

 plant turnips, potatoes, beet-roots, and carrots in the same, 

 or even in contiguous fields, but would distribute them 

 over his farm as widely as circumstances will allow. The 

 very worst case of the malady I ever saw was in a very 

 small field, where potatoes, beet-roots, and turnips, were 

 planted together. In this case the insects on the beets ex- 

 isted in countless legions. 



(482.) All remedies of this character, to be of any 

 value, must be universal ; as a partial attempt to remedy 

 contagion could be of but little benefit. The winged 

 insect can fly from field to field, from parish to parish, and 

 even from kingdom to kingdom ; and when it attacks it 

 multiplies with fearful rapidity. In order successfully to 

 attempt the extermination of this pest, therefore, a whole 

 country, or even all Europe, must devote its best energies 

 to the cause. An occasional obstinate, pig-headed farmer 

 ought not to be allowed to act contrary to the welfare of 

 the whole country ; and, perhaps, therefore, power might 

 very advantageously be given to churchwardens, or other 

 official persons, to adopt measures best calculated to cut 

 off contagion. 



(483.) The observations which I have just made have 

 appertained chiefly to the potatoe ; but it will readily be 

 seen that they apply equally to the prevention of contagion 



