W. A. Davis and G. C. Sawyer 355 



(Davis and Daish [191i]) that taka-diastase, the mixture of enzymes 

 isolated from Aspergillus oryzae, differs from the ordinary diastase of 

 malt extract mainly in containing maltase in addition to the ordinary 

 starch resolving enzymes. Taka-diastase therefore converts starch paste 

 completely into a mixture of maltose and dextrose, the latter rapidly 

 increasing in amount until 80-85 per cent, of the sugar is in this form. 

 We consider that the ordinary foUage leaf contains a mixture of enzymes 

 similar to that elaborated by Aspergillus oryzae, and of such a nature 

 that the maltase is always present in relative excess so that tiie maltose 

 formed by the breaking down of the starch is very rapidly and com- 

 pletely converted into dextrose. Now in our method of preparing the 

 leaf samples for analysis, the material was dropped into boiling alcohol 

 containing a little ammonia, so that the enzymes were destroyed instantly, 

 but Brown and Morris and most other workers in this field dried their 

 leaf material in an oven before extracting the sugars. During this drying, 

 owing to the large quantity of moisture in the leaf, the temperature 

 only rises gradually and the enzymes continue to act for a considerable 

 time before they are destroyed. Maltase is the first of the enzymes 

 to be put out of action ; it is well known to be one of the most 

 unstable of enzymes. Our experiments (Davis, 1914, i) with taka- 

 diastase show that it is largely destroyed before a temperature of 55° 

 is reached. When leaves are dried in an oven, after the maltase has 

 been destroyed at say 50° C, the ordinary diastatic enzymes continue 

 to act under optimum conditions as regards temperature and con- 

 siderable quantities of starch are broken down to dextrin and maltose. 

 This action lasts until the tem2:ierature rises to about80°, when the dextrin 

 and maltose-forming enzymes are also destroyed. As the maltase has 

 been completely killed in the earher period of drpng, the maltose formed 

 in this way will persist as such and be found in the mixture of sugars 

 subsequently extracted from the dried material. 



In support of this explanation of the differences between Brown and 

 Morris' results and our own, several facts may be adduced. In BrowTi 

 and Morris' experiments the proportion of starch in the freshly plucked 

 nasturtium leaf at the end of a sunny day was found to range between 

 2-9 and 7-4 per cent, of the total dry matter; we have always found the 

 starch in the same leaf to be considerably higher, thus in the example 

 given on p. 353, footnote, the starch was 17-6 per cent, of the total vacuum- 

 dried matter or about two and a half times the highest figure given by 

 Brown and Morris. In one case cited by these workers the starch was 

 found to be 4-59 and the maltose 5-33 per cent., the sum of the two being 



