EFFECTS PRODUCED BY PINK BOLIAVORM ON THE YIELD OF COTTON SEED. 303 



seed; and rarely more than about 20 per cent, loss in weight (crop conditions 1917). 

 The alteration to the ultimate percentage lint would also not be in the ratio, 

 percentage infestation : abnormal percentage lint :: percentage sound seeds : normal 

 percentage lint, but would be altered in the direction of the normal percentage 

 lint by the less weight produced by the damaged seeds. 



The differences in direction of variation of percentage lint of double and ordinary 

 damaged seeds would also tend to eliminate each other. All these factors together 

 help to keep the percentage lint close to what would have been the normal, if the 

 pink bollworm had been absent. 



In passing it may be remarked that the ginning outputs published for the last 

 few years have not shown any fluctuations which can be traced to damage done 

 by Gelechia. 



Tables XV and XVI have been compiled (from figures supplied by the State Domains 

 Administration, to whom our thanks are due), to show how far the percentage lint 

 in Mitaffifi and Affifi has varied during the period 1891-1917 and in Affifi, Assili 

 and Sakellarides in the period 1911-1917. 



Table XV. Variation in the Percentage of Lint of Sakellarides, Assili and Affifi 



Cottons ginned by the State Domains during the years 1911-1917, calculated 



from figures supplied by the State Domains Administration. 



Year. 



Sakellarides. 



Assili Sakha. 



Assili Qorashia 



Affifi. 



1911 



. 33-8 



35-6 



35-6 



33-9 



1912 



32-7 



35-4 



35'7 



33-9 



1913 



33-5 



36-4 



36-2 



34-5 



1914 



33-8 



36-2 



36-2 



34-0 



1915 



32 '8 



35-7 



35'5 



34-0 



1916 



31-5 



36-0 



34-7 



33-0 



1917 



341 



36-4 



36-7 



34-5 



Mean 



33-2 



360 



35-8 



34-0 



Sakellarides, ^ = 0-8; Assili, ^ = 0"5; Affifi, ^ = 05; for all varieties combined, 

 3=0-6. 



The figures for Mitaffifi and Affifi can be considered comparable to a great extent.* 

 The mean percentage lint for Mitaffifi is 34/0, for Affifi 34.' 1 ; the two series are 

 consequently extremely suitable for comparison and can be considered as forming 

 one unbroken series. 



The first point that calls for remark is, that for every year during the whole period 

 Qorashia ginnery has never given a lower percentage lint than Sakha ginnery, 

 and in all but two years it has given a higher percentage. 



The second point is that the simultaneous difference between the percentages 

 obtained by the two ginneries is often quite as large as or larger than the yearly 

 fluctuations from the mean percentage. 



The third point is that the standard deviation for Mitaffifi (period 1891-1912) is 

 twice as great as that for Affifi (period 1911-1917). As Mitaffifi was grown previous 

 to the introduction of Gelechia, and Affifi is contemporaneous with that pest, it is 



* See note at loot of Table XVI.— G.C.D. 



