July 15. 1919 Carbohydrate Metabolism in Green Sweet Corn 141 



the sides and transfer to the filter. With small portions of 50 per cent 

 alcohol, transfer to the filter any material still remaining in the flask; 

 after the alcohol has drained out of the filter, fill up once more with 

 50 per cent alcohol and drain. All sugars and any other reducing ma- 

 terials are now removed from the residue on the filter. The filter is 

 filled twice with 95 per cent alcohol and the residue allowed to dry on 

 the filter. The filter paper may be folded over the sample and placed 

 in small stoppered vials for another period of storage if necessary. 



The filter paper containing the sample was placed in a Kjeldahl flask 

 and covered with 200 cc. of water; sufiacient hydrochloric acid was added 

 to give a final strength of acid in the mixture of 2.5 per cent. Hydrolysis 

 was effected by boiling under a reflux condenser for three hours. 



A number of the filter papers used for the filtration were hydrolyzed in 

 the same strength of acid and for the same length of time as the samples. 

 Although the papers were claimed by the manufacturers to be starch 

 free, they were found to give a small amount of reducing material after 

 hydrolysis. However, the amount of this material was consistent in all 

 the boxes and in different parts of the box, so it was very easy to make the 

 necessary correction for the filter paper in the final results. The starch 

 was determined as glucose, but of course it includes any other poly- 

 saccharides which furnished reducing substances during the acid 



hydrolvsis. ■ 



EXPERIMENTAL DATA 



The work had not progressed far until it was evident that if the moisture 

 in the com at the time of picking had fallen below a certain percentage it 

 became a factor in controlling the rate of sugar loss. In order to eliminate 

 this variable factor, so that attention could be focused upon the tempera- 

 ture relation, the experimental ears were carefully selected to represent 

 a fairly definite stage of maturity — namely, the typical milk or best 

 eatable stage. Ears falHng below 80 per cent water were excluded from 

 the final calculations. 



The work of the first year was repeated on another crop the succeeding 

 year. The results of the two years' work are averaged in Table I. In 

 the experiments of the first year, the carbohydrate changes for each 

 consecutive 24-hour period were not determined in duplicate ears as 

 described for the experiments of the second year. Each percentage in 

 the table, therefore, is the mean of three ears, except in a very few cases 

 where the results of one ear were excluded on account of the moisture 

 content's falling below the arbitrary standard. The results of the experi- 

 ments at 5° and 15° C. are not given, as they add nothing to the general 

 conclusions. The average percentage of sugars in the corn at the be- 

 ginning and end of each storage period is indicated by (a) and (6), 

 respectively. 



