OTHER FARM CROPS 531 



Upland cotton (Gossypium hirsutum L.) forms more than 99 

 per cent of the cotton crop of the United States. The improvement 

 of this species has progressed along several different lines according 

 to the necessities or individual preferences of the grower, and very 

 distinct types have been developed, such as the stormproof cottons 

 of Texas, the earty cottons of North Carolina and Tennessee, and 

 the long-staple varieties of the Mississippi Valley. These diverse 

 types have led some to consider Upland cotton a composite of dif- 

 ferent species, and a recent author intimates that no less than seven 

 distinct species were concerned in its evolution. (B. P. I. B. 163.) 



Climate. The following are the essential features of a climate 

 adapted to the cultivation of cotton : The season must be sufficiently 

 long for the crop to mature. One of the most important factors, 

 therefore, is the probable date of the last killing frost in the spring 

 and of the earliest frost in the autumn, for cotton has a very long 

 growing period. Cotton picking is often extended far into the win- 

 ter, but the first killing frost of autumn checks the active growth of 

 the plant, and the blossoms or young bolls starting at this time will 

 not develop into mature fruit. The crop requires six or seven 

 months of favorable growing weather for its development. 



The next most important consideration is the amount and dis- 

 tribution of the heat and rainfall. Cotton is a plant which thrives 

 in a very warm or even hot atmosphere, provided the atmosphere is 

 moist and the transpiration is not so excessive as to overtax the pow- 

 ers of the plant. The temperature should be high and the daily 

 range uniform during the early growing period of the plant. The 

 mean daily temperature normally increases from the time the seed is 

 put in until about the first of August, after which it as rapidly falls, 

 making two distinct periods in the life of the plant. During the 

 first period of high and increasing temperature the plant should be 

 in full vegetative growth. Any great and sudden range in tempera- 

 ture, or any prolonged cold spell, is liable to check the vegetative 

 growth of the plant and tend to ripen it, which is very undesirable 

 during this stage of development. By the first or middle of August 

 the plant should have attained its full vegetative growth that is, 

 it should have stored up all of the food material it needs. From 

 this time on a decreasing temperature and a greater range of tem- 

 perature between day and night are favorable to the production of 

 a maximum crop, for this checks the vegetative growth and induces 

 the plant to convert the food material it has accumulated into fruit. 

 The soil also should be drier during this second period. 



As a rule the rainfall normally increases in the South from the 

 spring to the middle of summer, when it decreases, and the climate 

 during the autumn is usually remarkably dry and bracing. These 

 conditions are favorable to cotton production. During the earlier 

 period the rain should fall in frequent showers rather than in heavy 

 storms, and the very best seasons are when these showers occur at 

 night, giving with a large and well-distributed rainfall a large 

 amount of sunshine. 



