EFFECTS PRODUCED BY PINK BOLLWORM ON THE YIELD OF COTTON SEED. 301 



Table XIV. Showing Comparison of Sound and Attacked Samples. 

 Weights in Grammes. 



Description of Sample. 



Total weight 



with 



larvae. 



Total weight 

 without 

 larvae. 



Percentage 



Lint 



with 



larvae. 



3 



Percentage 



Lint 



without 



larvae. 



3 



30 sets of 100 sound 















seeds 





449-69 







34-2 ±0-08 



0-65 



30 random samples of 















about 150 grs. ea'-h. . 



4,3194* 



4,287-6 



34 7+0-09 



0-7 



34-9 ±009 



0-7 



30 sets of 100 damaged 















seeds other than 















'" double " ones 



282-93 



269-93 



35-6±0-19 



1-5 



37-3±0-18 



1-5 



30 sets of 50 double. 















seeds (= 100 seeds 















per set) 



31379 



284 66 



30-3 ±0-28 



2-3 



33-3 ±0-26 



2-15 



Gemmaiza crop ; sound 















bolls 



4 ? 777-4| 





34-0 ±0-02 



0529 







Gemmaiza crop ; dam- 















aged bolls 



15,226-0 





34-0 -4-0-01 



0-492 







Gemmaiza crop ; entire 















yield 



20,003-4* 



• 



34-0±0-01 



0-478 







* The total weight of 3,000 seeds with their lint would average 438-37. 



t The total weight of 3,000 seeds with their lint would average 496-28. 



j The total weight of 3,000 seeds with their lint would average 439-49. 



Note. — The first four samples were taken from a piece of land set aside for experimental 

 testing in this connection ; the last three refer to the ordinarv field crop on the same 

 farm. — G. C. D. 



It may be stated at once that all of these samples, with the exception of the 

 random ones, may be seriously biassed on account of sampling. In picking out the 

 sound seeds the operator may have unintentionally selected the largest, and in 

 selecting the damaged seeds a rather more than the average damage may be 

 expected as the standard. The " double " seeds are on the other hand probably 

 quite representative ; as, being rare, every one found would be retained, and as 

 they are fairly easy to recognise by feeling before ginning, all those encountered 

 would be kept. The only test we can apply for unbiassed sampling is by comparing 

 the total weight of the 3,000 seeds in question, with the average weight of 3,000, 

 seeds as calculated from the " Gemmaiza crop " figures, which may be accepted 

 as being quite free from bias, as will be seen later. The " Gemmaiza crop " samples 

 came from the same field as the others, but do not include them. 



From the comparison it would appear that the sound seeds selected were below 

 the average for " Gemmaiza crop " sound bolls. This was to be expected, if the 

 sampling was unbiassed, as in the seed cotton from which the seeds were selected 

 sound and attacked bolls were inextricably mixed together. In any case it may 

 be accepted that the good seeds selected were not above the average in weight. 

 Similarly it will be seen that the random sample varied very little (about 1'5 per 

 cent, only) in weight from corresponding quantities of " Gemmaiza crop " of the 

 same quality. This was expected in this case, as there was no reason for any 

 bias to be introduced. 



