WITH UErERENCK TO THE TO! ATO DISEASE. 63 



rapidly manifested. This was not the case in the previous dry 

 season. Had the weather proved dry in August, there is every 

 reason to suppose that the crop wouhl have been tolerably sound 

 and abundant. The disease, it is true, could be detected on the 

 underground portion of the stem in many instances in June ; 

 but notwithstanding this the fibres of the roots were sounder and 

 more abundant than in the two previous years, at the same period 

 of the season. 



The accompanying table contains statements of the produce of 

 a number of varieties cultivated in the usual way, but differing 

 considerably under the same circumstances in tlie amount of 

 sound produce; and I have to observe that tlie soundness of any 

 particular variety in one season is no sure criterion that the same 

 variety will be equally exempt from disease in another season. 

 For example, the Jersey Blues produced, in 1846, upwai'ds of 

 fifteen tons per acre sound, whilst in the present season their 

 return was scarcely half a ton of sound tubers. Other results in 

 the table are from varieties treated experimentally with reference 

 to the disease. All are given as tliey were actually weighed ; 

 and from tliese data the calculations per acre have been made. 

 The rate per acre not only affords a uniform standard of com- 

 parison, but likewise the most familiar iilea of the amount of 

 produce, sound and diseased. The results are numbered for 

 convenient reference. Tiie rows were everywhere 2^ feet apart ; 

 cut sets were employed, and planted 6 or 7 inches deep, and 

 about the same distance from each other in the rows. No 

 manure was applied ; but Nos. 1 to 36 inclusive were grown in 

 kitchen-gardtn soil previously manured for vegetable crops. 



In the results 1 to 5 tiie quantity of diseased tubers was 

 nearly double that of the sound. Crucksliank's Early, a variety 

 selected as aff<)rding a fair sound produce in former years, proved 

 the worst diseased in this quarter, in which Thurstone's Con- 

 queror yielded by far the best and largest amount of produce ; 

 but tliis, in its turn, may in another season yield the reverse, such 

 is the precarious nature of the disease. Many of Nos. 1 to 4 

 were totally rotten, so that it was impossible to take them into 

 account. 



The produce of No. 14, three rows of Jersey Blues, was little 

 more than 7 cwt. per acre ; No. 16, the same sort, produced only 

 half a ton sound. Tiie average of these four rows was 8 cwt. 

 62 lbs. sound, and 5 tons 19 cwt. 82 lbs. diseased per acre. An 

 intermediate row of Jersey Blues, treated according to Meyer's 

 method, gave at the rate of about 3 cwt. less of total produce per 

 acre ; but instead of only 8 cwt. 62 lbs., which was the average of 

 sound per acre afforded by the rows on each side of it, the sound 

 produce of Meyer's row, No. 15, was 2 tons 17 cwt. 57 lbs., or 



