Report on the Cultivation of Potatoes. 509 



facts which I have collected are given for the purpose of indi- 

 cating a possible reason why potatoes after a fallow-crop should 

 be comparatively free from disease. 



With the exception of Mr. Myatt and Mr. Knowles, all the 

 growers, as stated above, take potatoes either (1) after seeds, 

 which may have been down one or two years, or longer ; or (2) 

 after a white crop succeeding the ley. Five growers, however, 

 sometimes take potatoes after flax, beans, turnips, or mangolds. 

 Of these five, one has informed me that the potatoes are most 

 diseased after clover, and another that those planted on a wheat 

 stubble are more diseased than those taken after turnips. The 

 remaining three have not observed anv difference. 



The question thus suggests itself, — Is it possible that the pre- 

 ceding crop, whether clover, wheat or oats, or roots, beans, flax, 

 6cc., can produce any effect, whether prejudicial or beneficial, 

 on the succeeding potato-crop as regards the potato-disease ? And 

 if it can produce any effect, in what manner is it done, and what 

 is the rationale of the process ? 



There are some indications that the first question may even- 

 tually be answered in the affirmative ; and although at present 

 they are slight, I am very hopeful that they point in the right 

 direction ? 



I have already drawn attention to the practice of taking 

 potatoes after clover ; but I have not been able to describe the 

 result obtained in England by taking clover after potatoes ; and 

 I am told that in the north it is commonly believed that clover 

 will not grow after potatoes. However, at Grignon, in France 

 (the Government Agricultural College and Experimental Farm), 

 clover was sown, partly with wheat and partly with rye, in 

 1873, after a diseased crop of potatoes the previous year. This 

 clover was attacked by a fungus which the botanists could not 

 clearly distinguish from the potato-fungus ; and it is stated that 

 the clover was most diseased in those parts of the field where it 

 had been sown with wheat. The paper describing this result 

 has been translated by Mr. Carruthers, and will be found on 

 pp. 515-19, immediately following this Report. 



Again, with regard to the white crops which most generally 

 precede potatoes, viz. wheat or oats, it is remarkable, when read 

 in connection with the foregoing paragraph, that it is only two 

 years ago that Mr. Carruthers described in this Journal * a straw- 

 Ijlight, which had attacked a field of wheat on the farm of Mr. 

 H. J. Seels, of Wainfleet, Lincolnshire, as " the branching and 

 conjointed mycelium of a fungus, similar to that which has pro- 



Second Series, vol. viii., Part i., No. xv., 1872, p. 213. 



