820 
Journal of Agricultural Research 
Vol. XXI, No. II 
were lower in the late crop than in the early crop. The ripening processes 
proceed to nearly equilibrium positions independently of the rate of 
water loss by evaporation. On account of the cool, damp weather, the 
late crop came to the early dough stage with a relatively high percentage 
of water, making the percentage of starch lower than at the same stage 
in the early crop. By comparing the percentage of total sugar and 
starch based on dry weight and also the ratios of total sugars to starch, 
it will be noted that the late crop in the milk and early dough stages was 
not quite as far advanced in ripening as the early crop in the same stages. 
A smaller ratio of sugar to starch indicates a more advanced stage of 
ripening. 
SUMMARY AND CONCLUSIONS 
Based upon the nail test the ripening period of sweetcom was divided 
into four stages—the premilk, typical milk, early dough, and dough 
stages. The application of the nail test in classifying green corn into 
these four stages of ripening is described. 
The reliability of the nail test as a means of predicting the chemical 
composition of green corn at different stages of ripening is shown by the 
results of chemical analyses of the com after the nail test was applied. 
The reliability of the nail test is influenced by the rate of ripening and 
also by the rate of water loss by evaporation. 
The corresponding stages of crops ripening under different climatic 
conditions vary both in uniformity of composition and average percent¬ 
age composition. The percentage composition of the carbohydrates in 
the milk stage of a late crop was much more uniform than in the same 
stage of an early crop. 
The nail test is most reliable when applied to crops which ripen slowly 
in the cool autumn. These crops are most suitable for experimental 
work requiring the sampling of ears as nearly as possible at the same 
stage of ripening. 
In each of the ripening stages except the dough stages the percentage 
of total sugar was more constant than the percentage of starch. 
As ripening proceeds, the increase in the percentage of starch is much 
greater than can be accounted for by the decrease in the percentage of 
sugars. From the beginning of kernel formation until the end of the 
ripening period there is a continual movement of sugar from the plant 
into the kernels, where it is transformed into starch. 
