EXERCISE 55 



Fig. 73. A poor cotton plant 



A late unproductive plant ; the joints are long 



and the bolls are far out from the center or 



base of the stalk; the limbs have few joints 



and few bolls 



THE IMPROVEMENT OF COTTON 



Statement. Cotton, like all other domestic plants, is susceptible of improvement, and very rapid 

 strides have been made in this direction in recent years. As a result of natural variation, selection, and 



breeding there are many types, varieties, and strains of cotton, just 

 as there are of corn, apples, and strawberries. Much of this im- 

 provement has been made by selecting for propagation the best 

 of each season's crop. To make such selection intelligently, the 

 breeder must know what characteristics are of greatest importance, 

 and must be able readily to detect these characteristics in the field. 



Object. To develop further the cotton industry by learning 

 how to select the best cotton seed for planting. 



Material. A field of cotton ready to pick; a small balance; 

 pocket comb ; small ruler graduated to rfr inch. 



Directions. 1. Select five early- and five late-maturing plants. Com- 

 pare the two groups of plants as regards (a) the height at which the 

 first leaves are borne on the main stem ; (b) the length of the internode 

 on the fruiting limbs ; (c) the position of the bolls, whether mostly at 

 the top of the plant and on the outer end of the branches, or whether 

 they are borne mostly in the central and lower portions of the plant ; 

 (d) leafiness. 



2. Select twenty-five of the least productive plants and twenty-five 

 of the most productive plants in the 'field. Pick the cotton from each of 



the two groups of plants separately and weigh it. How many plants of each type would be required to give 



a yield of 1500 pounds of seed cotton or one bale of 500 pounds 



of lint? 



3. What is the average number of bolls per plant for each 

 group ? Pick the cotton from 100 large bolls and weigh it. Do 

 likewise for 100 small bolls. How many bolls of each class would 

 it take to yield 1500 pounds of seed cotton? 



4. Select five fully-open bolls, which in opening have per- 

 mitted the walls or burrs to curl backward to the extent of 

 allowing the seed cotton to be easily blown out by the wind. 

 Select also five fully-open bolls in which the burrs have not 

 curled backward 'sufficiently to make picking easy. Is there 

 any relation between the extent to which the burrs curl back- 

 ward and the thickness of the burr ? 



5. Select bolls showing each of the following defects : small- 

 size spots on the burr due to disease, imperfectly developed 

 lobes. 



6. Pick the cotton from ten bolls from each of five different 

 plants, keeping the five lots separate. Place these lots of cotton 

 in the sun and allow them to dry. Remove the seed from the 

 lint by hand. For each lot carefully weigh the seed and lint 

 separately. Is there any difference in the percentage of lint 

 produced by the different plants ? 



7. By means of the hands carefully separate the lint on a seed 

 of cotton into two equal parts without removing the lint from 

 the seed. Carefully comb the two portions of lint out straight 

 in opposite directions and determine its length. Compare different plants as regards the length of lint; 

 the color of the lint, and the strength of the fiber. From which should seed be selected ? 



[1101 



Fig. 74. A productive cotton plant, the sort from 

 which to select the seed for next year's crop 



