62 EXPERIMENTS WITH REFERENCE TO THE POTATO DISEASE. 



J oz. of sulphate of magnesia was given ; and also in that which 

 had 2 oz. of cliloride of lime. 



Toppi7ig the stems.— T&h\e V. 15. On the 17th of May, the 

 plants in 5 rows of the Early Champion were toj^ped. They 

 were then rapidly elongating in the same compartment with tlie 

 Cornish Kidney and Early Manly above mentioned. The rows 

 Avere each 10 feet in length. About two inches were cut off 

 from the extremity of every shoot. A corresponding extent of 

 adjoining rows was marked off at the same time ; but in this the 

 plants were not stopped. The amount of sound produce was at 

 the rate per acre of 6 cwt. 5 lbs. in favour of not stopping. The 

 operation of stopping must therefore be considered disadvan- 

 tageous. With regard to the pi'oportion diseased, the topped 

 plants had the advantage ; for whilst these had 9"56 per cent, 

 diseased, those not topped were diseased to the extent of more 

 than 13 per cent. 



To these experiments a few remarks may be added respecting 

 this year's disease in the Garden of the Society. 



The disease was watched in the potato-plants in the open 

 ground from an early stage of their vegetation. In the first 

 planted quai'ter, in the kitchen-garden, symptoms of disease were 

 observed in many of the plants almost as soon as they appeared 

 above ground, in the end of May. The parts of the plants 

 above ground were then, and for a considerable time afterwards, 

 exceedingly healtliy in appearance. From superficial observa- 

 tions they would have been pronounced, without hesitation, free 

 from all disease. Insects and fungi were looked for in vain by 

 many practised observers. On examination, the under-ground 

 portions of stems, instead of being white, were found to have 

 acquired a slight brown tinge ; sometimes this was almost uni- 

 versal, but more frequently on one side only, A rustiness, or 

 canker, ensued ; notwithstanding which the stems grew vigor- 

 ously. To prevent all attacks of insects, several rows had 

 powdered lime frequently scattered over them, commencing 

 when the plants had just got above ground. The lime em- 

 ployed was of the most caustic description, and reduced to 

 powder, not by slaking, but by grinding, being such as is pre- 

 pared in this manner for certain purposes of the builder. Tiie 

 disease, however, progressed in the plants limed similarly as in 

 those adjoining, which were not limed. Whether more or less 

 affected, the plants grew tall in the kitchen-garden quarters ; 

 yet their stems were not so generally destitute of axillary shoots 

 as was the case with those under the influence of the disease in 



