W. A. Davis and G. C. Sawyer 353 



snowdrop. It appears, however, that iu the later stages of growth 

 (September and October) certain gummy substances, which were not 

 studied in any detail, are formed as a reserve in the leaf tissue and appear 

 to be broken down to sugars at night, thus playing a similar part to 

 the starch in most foliage leaves. 



In view of the fact that we found, by using our method of 

 estimating maltose by maltase-free yeasts, that maltose is entirely 

 absent not only from the leaf and stalks of the mangold, which does 

 not store starch, but also from the leaves of many other plants which 

 form an abundance of starch, we considered it desirable, in order to 

 test Brown and Morris' views [1893] as to the part played by diastase 

 during the night in breaking down the starch to maltose, to study 

 the variation of the carbohydrates in the potato leaf throughout a 

 complete 24 hours period. The potato forms considerable quantities of 

 starch in its leaf and if, as seemed possible, maltose is an intermediate 

 stage in the synthesis of starch, just as it is in its degradation by enzymes, 

 it should appear in the leaf, at least in small quantities, during the day ; 

 if the starch is broken down by ordinary diastase in the way suggested 

 by Brown and Morris, maltose should appear in increasing quantities 

 at night during the disappearance of the starch from the leaf. Finally, 

 if Brown and Morris' view [1893, p. 673] is correct that maltose is the 

 translocation form of starch, maltose should be found in the stalks. 



Our experiments (see Tables I and II, p. 366) show that maltose 

 is entirely absent from the leaf and stalks of the potato at all periods 

 of the day and night. We have now made nearly 500 analyses by 

 means of maltase-free yeasts of many diiTerent kinds of plants, including 

 the nasturtium {Tropceolum majus), turnip, carrot, sunflower (Heliantkus 

 annuu-s), dahlia, Arum macidatum and vine (Vitis vinifera) ; iti no case 

 has maltose been found either in the leaf or stalks, even in such plants as 

 the turnip or nasturtium which store very large quantities of starch 

 in the leaf^. We need here only refer to the data given in a previous 

 paper (Davis and Sawyer [1914]) for the quantitative fermentations 

 carried out with the alcoholic extract of the turnip leaf (starch = 12-77 

 per cent, of the total vacuum-dried leaf). In order to work with as 



1 In one case (July 9tli, 1913) the leaf of the turnip was found to contain 18-73 per 

 cent, of starch calculated on the vacuum-dried matter left after extracting the sugars, 

 etc., with alcohol; this calculated on the total vacuum-dried matter of the leaf, including 

 the sugars, becomes 12-79 per cent. In a sample of Tropceolum leaf (July 4th, 1913) 

 the starch formed 26-75 per cent, of the dry leaf after extraction, or 17-6 per cent, of the 

 total vacuum-dried matter of the original leaf. 



