ROOTS. 145 



several years produced serious and increasing injury to the 

 potato crop, in 1845, almost threatening starvation in Ireland 

 and causing great loss and suffering in other countries. Its 

 effects have also been extensively felt in the United States. 

 Numerous and scientific examinations have been made on 

 the subject. The proximate cause is supposed to be a fun- 

 gus, but what are the reasons for its 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 10 

 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 potateos 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 may be plowed in the fall, or it may be left till late 

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

 and then turned under flat, and furrowed lightly to receive 

 the seed without disturbing the sod. Or they may be planted 

 by using a sharpened stake 3 inches in diameter, with a pin 

 or shoulder 10 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. We 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 inte- 

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

 F 



