Mar. i,i 9 2i Temperature Efficiency for Ripening of Sweetcorn 799 



ratio of total sugar to starch was adopted for this purpose. Table II 

 and figure 1 show the changes in percentage of moisture, total sugar and 

 starch, and also the changing ratio of sugar to starch in equal times for 

 the two seasons, starting with the same stage of ripening in both cases. 

 By comparing these ratios it will be noted that the late crop required 15 

 days to reach the same stage of ripening as the early crop reached in 6 

 days. In other words, the rate of ripening was two and one-half times 

 faster in the early crop than in the late crop. During this period of 

 ripening the starch content in the early crop increased from about 2.5 

 per cent to 10.5 per cent, and in the late crop from about 2.7 per cent to 

 10 per cent. At the end of this ripening period the sugar to starch 

 ratios were 0.556 and 0.500, respectively, and the chemical composition 

 was such that it probably represented the best edible stage. By the nail 

 test the corn was in the typical milk stage, but a subsequent paper will 

 show that the chemical composition of the corn changes considerably 

 during the so-called milk stage. 



Table II. — Comparison of early and late crops of sweetcorn in respect to changes in per- 

 centage composition in equal lengths of time 



Time from first 

 examination. 



Days 



O 



2 



4 



6 



8 



10 



12 



14 



15 



Early crop. 



Moisture. 



86-55 

 84.21 

 80.63 



75- 8 9 

 72.05 

 70.47 

 67.78 



65-5I 

 64.98 



Total 

 sugars. 



5-39 

 5-90 

 6.89 

 I 6.09 

 4.21 

 3- 75 

 3-5° 

 3-55 

 3.02 



Starch. 



2.47 



3-98 

 6. 92 

 10.95 

 15.90 

 16.93 

 18.98 

 20. 42 

 20.94 



Ratio of 

 sugar to 

 starch. 



187 



544 

 868 

 556 

 264 

 219 



183 

 170 

 149 



Late crop. 



Total 

 sugars. 



88.27 

 88.83 

 86.97 



85-56 

 85.21 

 83.80 

 81.56 

 79. 26 

 77.69 



6. 13 

 5-69 

 5-78 

 5-53 

 5-56 

 6.30 

 5. 62 

 5. 26 

 5.08 



Starch. 



Ratio of 

 sugar to 

 starch. 



2. 72 

 2. 32 

 2.86 



3-39 



3-8 5 

 5-48 



6. 90 



8.71 



10. 09 



2.300 



2 -459 

 2. 168 



1-747 

 1.448 

 1. 164 

 .879 

 • 673 

 0. 500 



1 Same stage of ripening as late crop on fifteenth day. 

 b Same stage of ripening as early crop on sixth day. 



EVALUATION OF CLIMATE TEMPERATURE EFFICIENCY FOR THE 

 RIPENING PROCESSES IN SWEETCORN 



Since both the early and late crops of corn were grown from the same 

 source of seed and on the same type of soil, the great difference in the 

 rate of ripening must have been due to the different climatic conditions 

 which prevailed during the ripening periods. Of the climatic conditions, 

 temperature was the most important variable. The averages of the hourly 

 mean temperatures for the ripening periods of the early and late crops 

 were 83 and 65 F., respectively. The ripening processes being either 

 chemical or dependent upon chemical processes, the prevailing tem- 

 peratures for the two periods would be expected to have a very different 



