METHODS OF SECURING SELF-POLLINATION IN COTTON/ 



By Rowland M. Meade, Scientific Assistant, Office of Crop Acclimatization and Adapta- 

 tion Investigations. 



The advantage of being able to prevent cross-pollination and thus 

 insure pure seed is recognized by all cotton breeders. Various meth- 

 ods have been used, both in this country and abroad. Some experi- 

 menters liave gone so far as to cover single plants with cages of fine- 

 mesh wire or cloth in order to prevent the visits of insects to the 

 flowers. This method may be very convenient when pure seed is 

 desired from a single plant only, but is scarcely practicable for whole 

 rows or bulk plantings. The expense of covering the plants is great, 

 and if the mesh of the screen is fine enough to exclude thrips and other 

 very small insects the conditions of growth are affected, so that the 

 plants may not develop normally. 



The method of bagging the flowers has been used most extensively. 

 A small paper bag is mflated and placed over a flower bud and the 

 mouth of the sack is tied with string or wire about the pedicel. 

 Flowers covered in this manner open naturally inside the sacks, and 

 the pollen is distributed from the anthers as freely as in uncovered 

 flowers. Within a few days after fertilization has been accomplished, 

 the paper sacks are again removed to allow normal development of 

 the young boh. The first operation of adjusting the sacks is one that 

 requires some time and skill, while the operation of removing the 

 sacks greatly uicreases the labor and requnes additional time. 



Another method has been described by Mr. W. W. Gilbert, of the 

 Bureau of Plant Industry, in the Proceedings of the American Breed- 

 ers' Association, vol. 8, 1912. Briefly, it consists of coiling a fine, 

 soft copper wire in a spiral about the enlargmg flower bud, making 

 one end fast near the base of the petals and bendmg the other end 

 double over the tip of the bud. This coil keeps the petals from open- 

 ing and the doubled end prevents the entrance of insects. The wire 

 falls away with the petals, which avoids a second operation like 

 that of removing the bags. 



The work of coiling and adjusting the wires can also be saved by 

 using other devices for holding the petals together. Dr. D. A. Saun- 

 ders, of this Bureau, has found it possible to use small rubber bands 

 instead of the coiled wires. The band is snapped over the upper end 

 of the flower bud and does not aflow the petals to open, but permits 

 sufficient expansion of the petals for the normal development of the 



1 Issued Apr. 12, 1913. 

 [Cir. 121] *^ 29 



