EXERCISE 54 



Fig. 70. Flower of upland cotton, showing sepals, petals, and stigma 

 (Courtesy of Bureau of Plant Industry, United States Department of Agriculture) 



A STUDY OF THE COTTON PLANT 



Statement. Cotton is the world's most important fiber crop. The cotton belt of the United 

 States produces more than two thirds of the world's supply of this staple. 



Object. To learn something of the con- 

 ditions of growth, form, structure, and 

 characteristics of the cotton plant. 



Directions. Carefully remove the soil 

 from the base of a growing plant containing 

 squares, flowers, green bolls, and open bolls. 

 Note the number, depth, and size of the 

 roots. What is the function of the tap 

 root ? Of the fibrous roots ? What would 

 be the effect of deep, close cultivation at 

 this time ? Note the size, height, and color 

 of the central stem. Describe its structure. 

 Study carefully the branches and distin- 

 guish between the fruiting and vegetative 

 branches. Of what use are the vegetative 

 branches ? At what place on the main stem are the longest branches produced ? The shortest ? How 

 are the leaves arranged on the stem? Are there differences in the shape, size, and arrangement 

 of the leaves on the fruiting branches and the vegetative 

 branches? Describe the cotton flower according to the fol- 

 lowing outline : (1) calyx — size, shape; (2) corolla — color, 

 size, shape ; (3) petals — number, separated or united ; 

 (4) stamens — number, position ; (5) pistils — number, 

 position. Make drawings as follows : (1) front view of bud 

 showing bracts and calyx ; (2) ventral view of flower with 

 bracts removed showing arrangement of calyx, calyx lobes, 

 and petals ; (3) draw a cross section of a half -grown boll 

 showing each part ; (4) make a collection of open bolls and 



classify them according to 

 their size, shape, number 

 and size of seed, amount and 

 length of fiber, and propor- 

 tion of fiber to seed ; (5) 

 make a collection of the 

 plants and open bolls of the 

 principal varieties of cotton 

 growing in the community 

 and compare them for earli- 

 ness, productiveness of lint 



and seed, and for length of fiber. Write a description of each, laying 

 emphasis on the advantages and disadvantages of each variety, and 

 kind of soil to which each is best adapted. 

 Questions. Which are the principal cotton-producing states of the Union? What is the highest 

 yield of cotton per acre in the locality and what is the average yield ? What is the lowest yield ? What 



. [108] 



Fig. 71. Stamens and stigma of 

 . Egyptian cotton 



(Courtesy of the Bureau of Plant In- 

 dustry, United States Department of 

 Agriculture) 



Fig. 72. A cluster of bolls from a prolific plant in 

 different stages of development 



(Courtesy of Ed. Kosch, San Marcos, Texas) 



