234 Studies in Indian Cotton 



of the method of cultivation may be calculated, for iu no case has the 

 same type been grown by both methods in a single season. In 1907 

 and 1908 all the pure types were grown in pots, while in 1909 they 

 were sown in the field. To obtain a comparison between the two 

 methods of cultivation it is necessary to resort to an indirect method 

 based on the crosses. In 1908 the entire F„ generation obtained from 

 the crosses was raised in pots while of the seed of these plants only 

 that of which a small amount was available was, in 1909, sown in pots, 

 the remainder being sown in the field. In Table XVI is given the 

 result of the comparison between the length of the vegetative period of 

 the offspring of plants having a similar period when these offspring are 

 grown under the two conditions. The difference due to the method of 

 cultivation varies from a minimum of 21 days to a maximum of 31 daj's 

 and, generally speaking, the greater the length of the vegetative period 

 the greater will be this difference. 



A similar result is reached from a comparison of Tables XVIII — 

 XXI. Tables XVIII and XX are based on the pot series and involve 

 only the seasonal difference between the two years 1908 and 1909, 

 which is fo^md to be five and three days respectively. In Tables XIX 

 and XXI, based on the field series, in addition to this seasonal differ- 

 ence there also occurs the difference due to the method of cultivation, 

 and the combined differences are in the two cases 31 and 28. By 

 subtraction the average difference due to method of cultivation alone is 

 found to be in the one case 26, and in the other 25 days. 



From the above it is noticeable that the difference iu length of the 

 vegetative period due to the method of cultivation is fairly constant for 

 all types, increasing only slightly with the increase of what may be 

 termed the standard vegetative period of the plant. The seasonal 

 difference, on the other hand, depends in considerable measure on the 

 type, being less for earl)' flowering than for late flowering types. While, 

 therefore, it is possible to reduce two series, differing only in the 

 method of cultivation, to one standard, this is not possible when a 

 seasonal difference enters into consideration. 



In addition to these two main causes, which, it will be noticed, 

 affect the entire series, the length of the vegetative period of individual 

 plants may be influenced through several minor causes and the actual 

 figures, though accurate in themselves, are thus rendered only appro.xi- 

 mate as a record of the standard length. Thus in a few cases the 

 young flower buds have been observed to fall without opening {vide 

 note to Table XVII) and an abnormally long vegetative period has been 



