166 



THE DEVELOPMENT OF RAW COTTON 



FIG. 20. VARIETY TESTING BY BOLLING CURVES. 



Illustrating the use of Plant-Development Curves for the comparison of 

 varieties, using very small amounts of seed sown in scattered groups 

 amongst ordinary field crop. 



The 1911 comparison was made on land which had borne three successive 

 crops of cotton, but was well cultivated. 



The 1912 comparison was one richer land, and the curves consequently 

 rise higher, but irrigation was delayed in July, causing shedding of 

 the flowers, which consequently reduced the yield for a while in Sep- 

 tember. 



In both years the slight lateness of the Voltos variety stands out, while 

 Sake! clearly cannot tolerate water-shortage. 



