180 



OBSERVATIONS AND EXPERIMENTS RELATIVE TO 



sort, and too near its natural period of decay, the plant could 

 not strike fresh roots, and of course the stem died. Three weeks 

 after it was first removed and replanted, the whole was again 

 taken up ; and the tubers were found thoroughly diseased in 

 consequence of remaining in contact with the decaying stem. 

 The brown colour pervaded their whole substance. 



From the above result, it was deemed expedient to try the 

 experiment of pulling up the stems of a portion of the planta- 

 tions of potatoes as soon as diseased blotches began to appear 

 upon them. Others were then cut over close by the ground ; 

 and some were left to die untouched. 



Where the potato stems were pulled up as soon as diseased 

 blotches began to appear upon them, the tubers were generally 

 free from blotches ; but where the haulm was allowed to remain, 

 many of the tubers in connection with it appeared to have ab- 

 sorbed putrescent sap, and exhibited blotches, as well as deeply 

 diseased substance. 



The potatoes cultivated in the garden were mostly samples of 

 rather early varieties. The sets were planted in good time, to the 

 depth of not less than six inches ; and the plants were well earthed 

 up. Before the blotching and decay of the stems and foliage be- 

 came manifest, a considerable weight of tubers had been formed, 

 notwithstanding the diseased action observed to have been going 

 on for a long time previous, and by which the successive formation 

 of tubers had been early arrested. Early sorts, such, for ex- 

 ample, as the Hative de Juin, distinguished under ordinary cir- 

 cumstances by its regularly-formed, roundish, and not large tubers, 

 to the number of six or more to the stem, had in many instances 

 only two or three ; but they were large, carbuncled, and, in 

 short, quite out of character, more like a coarse potato for cattle 

 than an early table variety. This irregularity of growth is of 

 course attributable to the disease having prevented any addi- 

 tional formation of tubers beyond the few that were first formed. 

 Instead of the substance elaborated by the tops being embodied 

 in many successively formed tubers, it could only be conducted 

 to a few, and these were consequently urged into an unnatural 

 development. In many cases unusual protuberances only were 

 formed ; but in others, a runner proceeded from the extremity of 

 the previously formed tuber, and a second tuber was produced. 

 In such cases it was found that the last formation contained 

 starch ; but scarcely any could be detected in the first, and they 

 boiled crisp. 



It must be observed with reference to the cutting off or pull- 

 ing up the stems when they exhibit symptoms of disease, that 

 although the operation was somewhat beneficial where the tubers 

 had previously acquired so much development as that above 



