EFFECTS PRODUCED BY PINK BOLLWORM ON THE YIELD OF COTTON SEED. 293 



from 10 sound bolls, 8 were found to weigh just two-thirds, or less than two-thirds, 

 the weight of the heaviest seed from the same boll, 4 weighed half and 2 weighed 

 only one-third the weight of the heaviest related seed. The standard deviation 

 was found to be 18 per cent, of the weight of the heaviest related seed. Thus, 

 expressed as percentages, 8 per cent, of the seeds from sound bolls differ by minus 

 more than twice the standard deviation from the weight' of the heaviest seed in 

 the boll in which they matured, 3 per cent, three times that amount and 1 per cent, 

 four times that amount. In the case of seed matured in damaged bolls the figures 

 are, 12 per cent, vary by more than twice, 8 per cent, more than 3 times, and 4 

 per cent more than 4 times the standard deviation from the weight of the heaviest 

 related seed. 



This increase in proportion of light weight sound seeds from damaged bolls, 

 as compared with sound seed from sound bolls, is most probably significant. 



B. The Germination of Sound Seeds from Attacked Bolls. 



In Table X are summarised the Tables for the germination of some of the samples 

 recorded in Table VII, arranged in groups of intensity of infestation from 5 to 65 

 per cent. (95 to 35 per cent, sound). 



Table X. To show the Correlation between the Intensity of Gelechia Attack and 

 the Germination of the Sound Seeds. 



Intensity of 

 attack. 



Number of 



samples 

 examined. 



Total number of seeds. 



Percentage 

 of 



Percentage of 

 sound bolls. 



Used. 



/ 



Germinated. 



germination. 



91-100 (95) 

 81- 90 (85) 

 71- 80 (75) 

 61- 70 (65) 

 51- 60 (55) 

 41- 50 (45) 

 31- 40 (35) 



64 

 28 

 38 

 20 



7 

 9 



2 



34,062 



16,354 



20,780 



11,674 



3,698 



3,638 



612 



31,654 



13,374 



17,033 



9,329 



2,184 



2,293 



255 



93 

 82 

 82 

 80 

 59 

 63 

 42 



Weighting as in Table VII ; r = 0-965 ± 0-017. 



The results show beyond possibility of doubt that the attack by Gelechia has an 

 effect on the germination of sound seeds from attacked bolls ; the correlation 

 being r = - 965 + 0'017. However, no such effect was recognisable from the 

 figures given in Table II. The reason for this apparent discrepancy is the same as 

 that given above, when discussing the progressive reduction of average weight 

 of the seeds that accompanies increasing Gelechia infestation. In both cases it 

 is the small seeds (which in ginnery tagawi are sifted out), that are the carriers of 

 reduced weight as well as of reduced germination. Besides this, the germination 

 is not seriously affected until about 45 per cent, of the seed has been attacked, 

 a degree of infestation not reached by the samples used in compiling Table II. 



