2cS4 



The Journal of Heredity 



selt-lcrlili/.ccl. Such an ananL;cnicnt 

 is shown in Fig. 17. Erect stamens, 

 c itlier loni;- or short, arc also favorahlc 

 to scU-lcrtiHzation, since they hring the 

 anthers in close proximity to the pistils. 

 Cotton bolls have three to hve locks 

 or compartments, each containint,' si.x 

 to eleven ovules, the number varying;- 

 with the type of cotton. I'vw locks oi 

 long staple types contain more than nine 

 seeds, while most oi those of big- 

 lolled, short, staple types have at least 

 eight seeds, but mature bolls in which 

 all of the seeds are fertile are rare. 

 In the bolls of Upland varieties lO^r? 

 to 25^0 of the ovules fail to develop into 

 seeds. 'i'here is usually a slighll\- 

 higher ])ercentage of aborted seeds in 

 the bolls of tl-.e long staple types. 



cor ION FLOWIK lYPKS 



Section of nn Ui)l;in(l X ICKyptinn cotton 

 flower on left, showing lon^ exserted i)islil. 

 Flowers of this type arc seldom comi)lel(ly 

 self-fertilized. Seetion of a short stai)le(l 

 Upland cotton flower on ri^ht, witli short 

 j)istil imbedded amfinji the stamens. 

 Flowers of this type are usually self-fer- 

 tilized. Enlarged tun ilianiclcrs to show 

 detail. (FiK- 17.) 



I..\k(;i: AMOf.XT OF rOLLKX NEEULl) 



It was found by i)reliniinary investi- 

 gation that the bolls failed to set unless 

 at least twenty-live grains of pollen 

 wrvv a]ti)]ied to the stigmas; even with 

 this number only one or two seeds 

 matured in each lock. As each lock 

 coiUains from six to eleven ovules, it 

 is necessary for at least twenty-live to 

 liftv-iive grains of i)ollen to reach the 

 stigmas in order that all the ovules of 

 a four or live-locked boll be fertilized. 



An experiment was condticted at San 

 .\ntonio. Tex., during 1913, to deter- 

 mine whether an increase in boll pro- 

 duction might be expected as the result" 

 of com])U'te pollination. 1\vo varieties 

 of cotton were chosen tor this investi- 

 gation — iJurango, a long, staple type 

 with stigmas exserted beyond the sta- 

 mens, and Acnla. a short, staple type 

 w ilh sliorl stigtnas embedded among tlie 

 stamens. The separation of the ati- 

 thers from the stigmas in the Durango 

 Mowers reduces the chance of self- 

 fertilization, while the conditions found 

 in .\cala cotton favor self-fertilization. 

 Two rows of each variety were i)lanted 

 foi" this experiment. 



i;.\i'i'ki Mi.xT i-.xi'r,.\ixs nii"i"r,i<i:xci-: 



( )nc of the rows of each varietv was 

 (lisignated as ._/ and the other as />. 

 The flowers in the A rows were com- 

 ])letely self-pollinated, anthers being re- 

 iiio\-ed b\- hand, and the pollen scattered 

 o\er the jnstil tmtil the stigmas were 

 well C(jvered. 'Jhe flowers in the B 

 rows were ;illowed to become pollinated 

 liatiu'all}-. 



A small string tag with the date of 

 opening of the blossom was seciu'ely 

 fastened about the branch at the base 

 of the flower to mark the ])osition of 

 e.nch flower that failed to develop into 

 a boll, 'i'he hand ])ollination in the .4 

 rows produced the etVect that might 

 be ex])ected from the work of bees or 

 other pollinating insects oi)erati!ig in 

 great numbers, except that the manipu- 

 latifin of the stigmas may h.ave bi'en 

 sligb.lly injurious, 'ihere wi're no indi- 

 cations of this, however, and. .as far as 

 possible, normal conditions wi-re pro- 

 \ided. 



