ROOTS. 171 



late rapid extension, and the remedy for its ravages, have not 

 yet been satisfactorily ascertained. 



Preventives of Rot. Under the following circumstances rot 

 has not appeared, when adjoining fields have been nearly de- 

 stroyed by it. 1. By using unripe seed, or seed which has 

 been exposed to the sun, light and air, and well dried for ten 

 days after digging, and afterwards stored in a dry place in 

 small parcels, where air. is excluded till the moment of plant- 

 ing. 2. By the use of lime, some of which is placed in the 

 hill and the potatoes dusted with it, and also from the use of 

 charcoal and salt, gypsum or other salts. 3. By the absence 

 of fresh barn-yard manure, or if used, by adding largely of 

 lime or saline manures. 4. The use of fresh sod, which has 

 long been untilled. This has been found more efficacious 

 than any other preventive, although it has occasionally failed. 

 The sod rriay be plowed in the fall, or left till late in May 

 or early in June, when it has a good coating of grass; 

 then turn over the ground and furrow it lightly, to receive 

 the seed wit.hout disturbing the sod. Or they may be planted 

 by using a sharpened stake three inches in diameter, with a pin 

 or shoulder ten inches from the bottom, on which the foot may 

 be placed for sinking the holes. These should be made be- 

 tween the furrow slices at the proper distance for drills, and 

 a single potato placed in each, which may be covered with 

 the heel. 5. Sound, early varieties, early planted, have also 

 escaped. I have thus secured a good yield, almost wholly 

 free from disease ; and even those affected did not appear to 

 communicate disease to others. It has also been found that 

 some very late planted have escaped rot ; and if it be an epi- 

 demic, it may be, that both by early and late planting, the 

 peculiar stage of vegetation when the fungus appears, is in a 

 great measure avoided. But the investigations on this impor- 

 tant subject are still in their infancy, and nothing has thus 

 far been ascertained, which can be justly considered as hav- 

 ing determined principles of universal application ; yet it is 

 to be hoped that the zeal, intelligence and general interest 

 which are now combined for this object, will ere long de- 

 tect, what has hitherto evaded the severest scrutiny of scien- 

 tific research. 



Arresting the disease has in some instances been successful, 

 by mowing off the tops when they are found defective. This 

 practice would be injurious to healthy plants, but may be 

 adopted, like that of cutting grain when struck by rust, if it 

 will secure even a part of the crop. When disease appears 



