242 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



plus the citric acid were introduced directly into 50-cc. centrifuge 

 tubes and placed in a boiling water bath for 10 minutes, after 

 which the acid was neutralized to phenolphthalein with normal 

 sodium hydroxide, Fehling's solution added, and the balance of 

 the process completed by the Shaffer method. The sucrose was 

 then determined as glucose by the increase in the cupric-reducing 

 power of the solution, due to inversion of the sucrose. 



Starch determinations .—The material from which the sugars 

 had been extracted was used in the starch determinations. 

 This was usually sufficiently dried by standing in the air for a 

 few hours so that it could be ground up finely in a mortar. It 

 was then carefully weighed and exactly J of it measured out, 

 made into a paste by adding a small amount of water, and the 

 paste poured into 400 or 500 cc. of boiling distilled water. Then 

 the starch which had been centrifuged out of the sugar solution 

 was suspended in 100 cc. of distilled water, and 20 cc. (|) 

 pipetted out and added to the other. The whole was then 

 gelatinized by boiling under a reflux condenser for two hours, 

 cooled, and made up to one liter with distilled water, 2 per cent 

 toluol being added to prevent the growth of microorganisms. 

 One-tenth gm. Taka-diastase was then added to 100 cc. of the 

 solution, which was well shaken during sampling, and this was 

 incubated at 45° C. for 24 hours. Under these conditions, 

 according to Davis and Daish ('14), hydrolysis of the starch is 

 complete, it having been broken down into glucose and maltose, 

 which exist in a definite ratio in the solution. These sugars 

 were then determined as glucose. The value found, of course, 

 is not the true starch value, but may be used as a basis for com- 

 parison, which is all that is demanded in this work. 



Results and Discussion 



Diastase activity .—The results of the diastase activity deter- 

 minations are given below (table i) . These results are, of course, 

 comparative only. The figures in the first three columns 

 represent the number of cubic centimeters of potassium perman- 

 ganate used in titrating the dissolved cuprous oxide in one 

 sample, while the relative enzyme activity (the difference be- 

 tween the figures in the first and third columns) is given in the 



I 



