1919. \ 



BAINFALL AND FliOGHOPPEE BLIGHT. 



15T 



DISTRIBUTION OF RAINFALL DURING THE YEAR. 



Even in countries like Trinidad, in which, as has been shown, 

 the total rainfall during the year is not a limiting factor of the crop,, 

 that rainfall may be so distributed that there may be an excess at one 

 period of the year and a deficiency at another. 



The normal seasons in Trinidad consist of a dry season lasting 

 usually from January to the middle of May, during which the rainfall 

 is generally below three inches per month, and a wet season from June 



* 



.5 



4.1 



5 



<5 . 



TB1NIDAD^'RA\NFAU 



" 18 62. ?_I9JI^. 



|u fib Hcu/ Q»>- I»Uy iw>t jul^ C^ S||, Qd- 



K«i 



T5S^ 



Fig. 5. 



Fig. 5. —Monthly rainfall, Trinidad Botanic Gardens, average of fifty-three j-ears. 



to December in which the rainfall is usually over five inches per month.. 

 Fig. 5 shows the average monthly rainfall at the Botanic Gardens,, 

 and St. Clair Experiment Station, Poi-t-of-Spain, for fifty-three years 

 continuous observation. W 



There is however one feature that is not so distinctly emphasised by 

 the average curve as in reality. In nearly every year a dry period of 

 longer or shorter duration occurs during August, September or October 

 and is known locally as the " Indian Summer." An examination of the 

 monthly records averaged in the above figures shows that this drop in 

 the rainfall was distinct in about 35 out of the 53 years under consi- 

 deration, the rainfall being below five inches four times in August, 

 eight times in September and thirteen times in October. 



This Indian Summer is one of the most important features of the 

 rain distribution and has, as will be shown, a marked effect on the 

 sugar crop and particularly on the prevalence of blight. Owing however 



(1.) 1852 to 1899 at tlie Royal Botanic Gardens, and 1900 onwards at the closely 

 adjacent St. Clair Experiment Station. 



