CH. YIII.] THE DISEASES OF PLANTS. '275 



I specify these quantities as those I calculate to he 

 the most correct, yet in all experiments it is best to 

 try various proportions. Three or four bushels may 

 be found sufficient, perhaps twelve, or even twenty 

 may not be too much. 



Frequent hoeing has been recommended as a pre- 

 ventive of this disease ; but I believe tliis to be un- 

 sustained by either reason or practice. Hoeing, like 

 any other stirring of the surface soil, assists the ad- 

 mission of the atmosphere to the incumbent plants, 

 and so far promotes then- general health ; but I have 

 never yet found, or even heard any one advance, that 

 a frequently hoed part of a crop was free from the 

 ambury, which affected the more rarely hoed portion. 



It would be fortunate if our white turnip crops 

 could be sown as early as our Swedes, for they would 

 then, probably, be as little liable to the ambur}' as 

 these are. The reason of this seems to be, that the 

 weevil does not emerge into that state in which it is 

 capable of injuring the young plants until the sum- 

 mer is far advanced, and by that time the Swedish 

 turnips have attained a size which secures their 

 safety. I conclude this to be the case from my own 

 slight, very slight, observ^ations upon the habits of 

 the insect ; for, unfortunately, we are veiy deficient 

 in knowledge upon this point. It is to be regretted, 

 that entomologists are not more attentive to what 

 may be termed the private and particular histor}^ of 



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