158 



THE DEVELOPMENT OF RAW COTTON 



be about 30 per cent, larger if it were not necessary to 

 put the rows far apart so that horse-hoes could work 

 between them. 



Taking three controllable variables only manure, 

 so wing -time, and spacing a good deal of most practical 



Week 



Ending Aug. 2 



Sep:6'. h Oct.4- 1 



FIG. 19. IDENTICAL PLOTS OP COTTON. 



These curves show the number of bolls opening in each week of the season 

 on five plots which were nominally exactly alike, in various parts of 

 a single acre of land J (shown in PI. XI., XII.). Perfectly definite 

 differences exist between them throughout the season, due to variation 

 in the deeper layers of soil. 



Fig. 2, p. 24, is constructed from the averages of such sets of five plots. 



Variety, Domains Afifi; site, Giza, 1913. 



MEAN YIELD = 400 POUNDS OF LINT PER ACRE. 



information can be obtained in a single year. It remains 

 to consider how the optimum for each of these variables 

 should be ascertained, and this brings us to the question 

 of experimental plots. 



