RUST AND MILDEW IN INDIA. 



nearly so reduced as the corresponding Jeypore grains, twenty of 

 them equalling in weight the ten sound Jeypore grains. In this 

 case, therefore, there was a loss of 100 per cent. These data are not, 

 of course, absolute indications of the harm done by the parasite to 

 each plant attacked; they are quoted only to show that the disease 

 has most destructive results. The amount of loss occasioned in 

 the ears of individual plants must depend upon the period of its 

 life at which it was attacked, the extent to which it is attacked, 

 &c, these again depending on weather, soil, and other conditions. 



It has also occurred to me that some presumptive evidence 

 might be obtained of the prevalence and influence of rust and 

 mildew in India, by comparing the outturn of wheat for a series of 

 years, in those provinces in which the fungus certainly exists, with 

 the climatic conditions prevailing during the earliest months of the 

 year, when the wheat plants are in the stage of existence most 

 liable to attack. Dr. George Watt, C.I.E., has kindly given me a 

 tabular statement showing the price of wheat (seers per rupee) 

 for the 29 years, 1801-89, in the Central Provinces, Punjab, and 

 North-West Provinces and Ondh ; and as this appeared to me to be 

 a good index of the outturn of grain for each year, I have thrown 

 the results into a graphic form in Table I. Unfortunately, 

 meteorological data are available to me only from 1875. From a 

 summary of meteorological conditions, prepared annually for the 

 Sanitary Commissioner with the Government of India, I have ex- 

 tracted the data necessary for my purpose, and have exhibited them 

 in Table II. The weather during January, February and March 

 is most important in this connection, not only because it has a 

 maximum effect on the growth of the wheat plants themselves, 

 independently of any fungal attack, but also because this is the 

 season during which the parasite usually attacks these plants. 

 The humidity of the air, the cloud proportion, and the rainfall, are 

 the most important factors. A combination of all these in slight 

 excess (except perhaps cloud) is, I presume, favourable to the 

 growth of the host (wheat plants), and is certainly (especially in- 

 cluding cloud) favourable to the growth of the fungus. Now, if in 

 any year we find that these climatic conditions were favourable to 

 the growth of the wheat plants, but that the outturn of wheat was, 

 nevertheless, poor, we may with some plausibility attribute the 

 deficiency of outturn to the repressive influence of the parasite ; 

 for otherwise I do not know how the deficient outturn could 

 be accounted for. In order to render the meteorological data 

 readily comprehensible, and comparable with the graphic repre- 

 sentation of the outturn of wheat each year, I have arranged them 

 in a compressed tabular form, indicating excess over the average by 

 X, and deficiency by D; whilst a normal condition is represented by 

 N. Wherever a very decided condition, either of excess or 

 deficiency, was noted in the meteorological report, I have enclosed 

 the letter X or D within a circle. In a few instances the condition 

 was not clear, and in such cases I have inserted a mark of 

 interrogation. 



Before proceeding to a comparison of the outturn with these 



