Environmental Factors and Hereditary 



Differences Influencing Fruiting of Cotton 



IN 1911, observations were be- 

 gun by E. C. Ewing at the 

 Mississippi Experiment Station 

 in a study of the processes by 

 which the fruit is normally set and 

 matured in American Upland cotton in 

 that locality. "The project also con- 

 templated a study of the differences in 

 the fruiting processes displayed by dif- 

 ferent varieties growing under similar 

 conditions. The object of the investi- 

 gation was to obtain a better under- 

 standing of the seasonal history of the 

 cotton plant for consideration in the 

 light of the information already avail- 

 able in regard to the life history and 

 habits of the cotton boll weevil, and es- 

 pecially to determine the nature of 

 varietal differences in the fruiting proc- 

 esses. In the same year experiments 

 were started with the view to the im- 

 provement of varieties and the produc- 

 tion of new varieties for culture under 

 boll weevil conditions. This effort to 

 take stock of the material and qualities 

 available in the existing varieties then 

 appeared essential for the proposed cot- 

 ton-breeding work. 



"The fact that boll weevils usually 

 emerge from hibernation in numbers 

 relatively small as compared with the 

 numbers appearing in late summer and 

 fall and that only the early fruit can 

 mature uninjured in infested fields, 

 pointed in the early exi)cricnces with 

 the \k)\\ weevil to the importance of 

 earliness as a varietal characteristic in 

 cotton to be grown under boll weevil 

 conditions. But from the nature of the 

 cotton plant it became evident that 

 earliness is a rather indefinite matter, 

 that hereditary (jualities might contri- 

 bute to earliness, and that these quali- 

 ties might be closely related or might 

 be independent f)f one another. These 

 and numerous other collateral questions 

 have been studied, and the results and 

 conclusions are comprised in this re- 



.^72 



port. [Technical Bulletin, No. 8, Ag- 

 ricultural College, Mississippi, June, 

 1918, pp. 93.] 



THE OUESTIOX OF EARLINESS 



"The effects of external influences, 

 including certain cultural factors, have 

 been referred to under several head- 

 ings, and the hereditary qualities which 

 constitute varietal differences in earli- 

 ness have been discussed to some ex- 

 tent. In that discussion it was pointed 

 out that a variety might be early in one 

 way and late in another. Eor example, 

 two varieties planted and grown alike 

 may produce their first flowers on the 

 same date, in which case they are 

 equally early in one phase of earliness, 

 initial flowering. But more time may 

 be required for the bolls of one of these 

 varieties to develop than for those of 

 the other. If the mean boll period 

 at the beginning of the fruiting season 

 is forty-five days for one variety and 

 fifty days for another, then the first 

 bolls of the former should open five 

 days earlier than those of the latter, 

 although the first flowers appeared sim- 

 ultaneously in both varieties. Then the 

 amount of fruit set within a given pe- 

 riod, say thirty days after flowering be- 

 gins, depends first on the mean rate of 

 flowering, one or two or three flowers 

 per day as the case may be, and second, 

 on the percentage of these flowers lost 

 through shedding. The last two factors 

 also, of course, help to determine the 

 rate at which the bolls open in the 

 autumn and the relative earliness of the 

 crop of any variety. Thus, these four 

 factors, the time of commencement of 

 flowering, the length of the develop- 

 mental ])cri()(l of the boll, the rapidity 

 of flowering, or the daily rate of flower 

 production, and the percentage of shed- 

 ding, together with the mean, yield per 

 boll, are all more or less related to the 

 question of weevil injmy and weevil 



