ENVIRONMENT OP THE BOLL 115 



Therefore the maximum effect on lint length is obtained 

 when the boll is 15 or 16 days (48-32=16) old at the 

 time of watering, while if the boll is more than 21 days 

 old (48- 27= 21) it is unaffected. 



This result is different in degree from that which we 

 obtained in the previous series after the long water 

 starvation, and it indicates that in this case we are deal- 

 ing with a simple and straightforward limiting factor 

 effect, instead of the complicated poisoning effect. In 

 this case the effect of watering is simply to allow the 

 lint hairs to grow more during the last few days than 

 they would otherwise have done. The general principle, 

 that the maximum effect is produced round about the 

 fifteenth day of boll development, is the same as before, 



Turning now to the strength curve, we may first note 



that it is immaterial for general purposes whether the 



strength is determined by breaking single 



hairs, or whether bunches are tested by 

 Lint. 



impact. The impact figures obtained in 



this series cannot be converted directly into breaking 

 strains for direct comparison with the previous series, 

 but some determinations of the breaking strain made 

 tediously by hand in the absence of the author's auto- 

 matic tester (PL XVI.) indicate that the maximum 

 strength attained in this series was rather higher than 

 the maximum attained in the former series, just as in the 

 case of lint length. Moreover, whereas the former maxi- 

 mum was rather spasmodic, the strength in this series 

 under good field conditions is maintained steadily for 

 several days at a time. 



