FARM CROPS. 105 



the tropics of both hemispheres. Very early writers 

 refer to it as tree wool. It is probable that it was 

 carried from Asia to Egypt, and from there to Eu- 

 rope in early times. Its rapid growth in favor to the 

 position of the most important fiber crop of the world 

 covers a period of but little more than a century. The 

 invention of the cotton-gin in 1793, for separating the 



A FIELD OF COTTON. 



lint from the seed, caused a sudden expansion of the 

 cotton-growing industry. 



Region of Cultivation. Cotton can be grown more 

 or less successfully in any latitude where the period of 

 exemption from frost is five and half to six months, 

 and where favorable soil and moisture conditions are 

 to be had. It thrives best in well drained mixed soils. 

 The territory of the United States south of the thirty- 

 seventh parallel and east of El Paso, Texas, offers the 



