44 



BULLETIN 1134, TJ. S. DEPARTMENT OF AGRICULTURE. 



for the first pollination in some cases pollen of the same variety, in 

 other cases pollen of the other type. Progenies from the resulting 

 bolls were grown in 1911. The percentages of hybrids obtained from 

 the various pollinations are shown in Table 25. 



Table 25.- 



-Hyorids resulting in 1911 from double pollinations of Egyptian and 

 upland cotton floioers at Yuma, Ariz,, in 1910. 





Egyptian as the 

 female parent. 



Upland as the 

 female parent. 



Method of. pollination. 



Plants 

 grown. 



Percent- 

 age of 

 hybrids. 



Plants 

 grown. 



Percent- 

 age of 

 hybrids. 





164 



18 ±2.0 



158 



32 4-2.5 







Egyptian pollen applied first, upland pollen 15 minutes later. . . 

 Egyptian pollen applied first, upland pollen 30 minutes later. .. 

 Egyptian pollen applied first, upland pollen 60 minutes later . . . 



184 

 146 

 151 



8 ±1.3 

 14 ±1.9 

 13 ±1.8 



142 I 56 ±2.8 

 160 24 ±2.3 

 121 ! 59 ±3.0 







11.7±1.0 



46.3±1.6 









Upland pollen applied first, Egyptian pollen 15 minutes later. . 

 Upland pollen applied first, Egyptian pollen 30 minutes later. . 

 Upland pollen applied first, Egyptian pollen 60 minutes later . . 



118 

 123 

 166 



5 ±1.4 

 10 ±1.8 

 7 ±1.3 



107 ! 51 ±3.3 

 93 36 ±3.4 

 107 ; 47 ±3.3 







7.3± .9 



44.7±1.9 











1,052 



i 



10. 8± .6 



8SS 42.3+1.1 









The data given in Table 25 show no consistent differences in the 

 percentages of hybrids depending upon whether pollen of the same 

 or of the other variety was applied first or upon the length of the 

 interval between the application of one and the other pollen. When 

 Egyptian cotton was used as the female parent, deferring the appli- 

 cation of the upland pollen until one hour after the Egyptian pollen 

 was applied resulted in an apparent reduction in the percentage of 

 hybrids as compared with that resulting from simultaneous applica- 

 tion of the two pollens, but the difference was not significant. On 

 the other hand, deferring the application of the Egyptian pollen until 

 an hour after the upland pollen was applied, so far from increasing 

 the percentage of hybrids, resulted in an apparently significant de- 

 crease as compared with the percentage from simultaneous applica- 

 tion. With upland cotton as the female parent the percentage of 

 hybrids when application of the Egyptian pollen was deferred one 

 hour was significantly greater than in the case of simultaneous ap- 

 plication of the two pollens, but a much greater and more significant 

 increase in the percentage of hybrids resulted from deferring appli- 

 cation of the upland pollen until one hour after the Egyptian pollen 

 was applied. These results are inconsistent and seem inexplicable, 

 but at any rate they increase the probability that the slight differ- 

 ences, under natural conditions, in the time of the arrival of self 

 pollen and of foreign pollen, as noted on a preceding page, are of 

 little consequence in determining the relative degree of self-fertiliza- 

 tion and of cross-fertilization. 



The total number (1,052) of Egyptian flowers which were double 

 pollinated in the McLachlan experiment yielded 10.8 ± 0.6 per cent 

 of hybrids, and the total number (888) of upland flowers yielded 

 42.3=tl.l per cent of hybrids, the latter figure representing only a 



