(Vol. 6 

 248 ANNALS OF THE MISSOUHI BOTANICAL GARDEN 



value found in the case of tubers 2 cm. in diameter does not 

 follow the general trend, and remains unexplained. The two 

 samples of seed potatoes exhibit a rather wide difference in 

 starch content, which, the author believes, is perhaps due to 

 varietal differences or to a difference in the conditions under 

 which the potatoes were kept. The conditions under which 

 the tubers were grown may also have exerted some influence in 

 this respect. 



Summary 



A review of the literature, bearing directly or indirectly upon 

 the subject of this paper, is presented. 



The methods of experimentation are described. They include 

 the determination of diastase activity of potato tubers at various 

 stages of development by adding fresh potato juice to a solution 

 of soluble starch ; the extraction and estimation of reducing sugars 

 and sucrose by the comparatively new method of Davis, Daish, 

 and Sawyer; and the estimation of starch by means of Taka- 

 diastase. 



The following results were obtained : 



Diastase activity and starch content were found to increase 

 with advance in the development of the tubers. 



In general, the increase in enzyme activity and starch content 

 of growing potatoes was accompanied by a decrease in the total 

 sugars present. 



When the juice of potatoes was preserved with toluol and kept 

 for 24 hours at room temperature, its diastatic activity was found 

 to decrease quite markedly. 



Evidence was obtained which indicates that a co-enzyme is 

 necessary in the hydrolysis of stanch by potato diastase. The 

 activating agent exists in the juice, and is not destroyed by boil- 

 ing, nor is it precipitated by alcohcl. 



It is the opinion of the author that if a number of analyses 

 were made along the lines described and the average of these 

 taken the comprehensive results thus obtained would clear up 

 the points which, in this report, appear somewhat doubtful, 

 and would make it possible to draw definite conclusions. 



The writer wishes to acknowledge his indebtedness to Dr. 



