78 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



Fibre Expert to the Government of Bengal. It has been 

 noticed during the last few years that the incidence of wilt 

 in the permanent manurial experiments on the farm varies 

 greatly in the different plots, being less in those that have 

 received no manure and more in those that have had mineral 

 fertilizers. This occurred in both series of the experiments 

 and was too clearly marked to be accidental. Its examina- 

 tion has been taken up in the hope that it may throw some 

 light on the obscure problem of resistance and susceptibility 

 to fungous diseases in plants. The cropping hostory and 

 soil composition of these plots are particularly well known, 

 and they have received uniform treatment for the past 

 eleven years, so that they are very suitable for the purpose. 



Two possibilities suggest themselves : either the treat- 

 ment of the plots has in some way altered the composition 

 or characters of the host plant, or it has influenced the 

 parasite. If the former, it should be possible to correct the 

 deleterious effect of the mineral fertilizers by appropriate 

 manurial treatment, since it is presumably nutritional.. 

 For this purpose a second series of permanent manurial 

 experiments has been laid down and artificially infected so 

 as to produce a heavy attack of wilt in all the plots in the 

 first year. If the condition depends on some effect of the 

 mineral fertilizers on the parasite (which is a soil fungus), 

 it should be possible to detect this by regarding the soil as 

 a culture medium and examining its effects on the vigour or 

 virulence of the fungus. For this purpose pot cultures with 

 soil from the permanent plots have been started and have 

 already given some interesting results. Attempts have also 

 been made, hitherto without success, to determine quantita- 

 tively the amount of the parasite in the soils of the differ- 

 ent plots, and it is proposed to test the effect of the soil solu- 

 tion on the growth of the fungus. Mr. Finlow has mean- 

 while carried out a complete ash analysis of the plant from 

 several of the plots. The root development under different 

 manurial treatments is also being examined. It is not 

 expected that definite results will be obtained before several 

 years. 



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