[Vol. 6 

 238 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



hydrolysis of starch was believed to be effected by a mixture of 

 enzymes, containing maltase in relative excess, so that the 

 transformation of starch to dextrose was complete. 



The conclusions in regard to sucrose are in agreement with 

 the views of Brown and Morris ('03). The absence of maltose, 

 however, is contrary to the findings of the latter authors, and is 

 due, according to Davis, Daish, and Sawyer, to the fact that 

 enzyme activity was not checked promptly in the material 

 examined by them. Disagreement also exists in regard to 

 pentoses, Brown and Morris not finding these sugars present. 



Materials and Methods 



Potatoes of the Irish cobbler variety were used in this work. 

 They were grown on a bench in the greenhouse, and, as is usually 

 the case under such conditions, the mature tubers were small, 

 the largest being only 6 cm. in diameter. It was the aim at the 

 outset to make analyses of the tubers for enzyme activity, 

 reducing sugars, sucrose, and starch, beginning when the young 

 potatoes had attained a diameter of 1 cm., and making later 

 determinations corresponding with each increase of 1 cm. in 

 diameter until maturity. This plan has been followed with the 

 exception that it was not possible to obtain sufficient tubers of 

 the first size (1 cm. in diameter) for the determinations of both 

 diastase activity and carbohydrate content, but enough were 

 found for the enzyme activity determinations. Some analyses 

 were also made of seed potatoes. 



Upon reaching the proper size the potatoes were harvested, 

 washed free from all particles of dirt, and dried with a towel, 

 after which the analysis of the material was begun without 



delay. These and all other operations were carried out as 

 quickly as possible, so as to avoid errors which might be due to 

 delay in handling. 



This procedure may be objected to by some on the ground 

 that size of the potato tuber is not necessarily correlated with 

 stage of development. In these experiments, however, the first 

 four sizes (1-4 cm. in diameter, inclusive) were all dug at the 

 same time, while the vines were still actively growing, and the 

 5- and 6-cm. sizes were secured about two weeks later. All 



