34 



plants were examined^ some of which, such as potatoes, turnips, 

 Tropcsolum, and sunflowers, elaborate large quantities of starch in the 

 leaf during the daytime to be used as a reserve during the night ; 

 while others, such as mangolds, dahlias, and the grape vine, store 

 reserve carbohydrates other than starch (saccharose, inulin, and 

 glucose). 



Unless we decline to accept the view that the starch breaks down in 

 the usual way to maltose we must suppose that the enzyme maltase 

 is present, which decomposes the maltose as quickly as it is produced. 

 Evidence is adduced in favour of this supposition, and the view is put 

 forward that the transformation of the starch proceeds on the following 

 lines : 



Starch — soluble starch and dextrines (by Liquefying enzymes.) 



Dextrines — maltose (by Dextrinase). 



Maltose — glucose (by Maltase). 



The failure of other workers to find maltase is attributed to its 



instability, it being readily decomposed by alcohol or chloroform, and 



to the circumstance that it is endo-cellular and therefore not easily 



extracted by water. Beyerinck's results indicate that the maltase 



s mainly localised in the aleurone layer of the endosperm. 



XXIII. " The Distribution of Maltass in Plants.'' II.—" The 

 Presence of Maltase in Foliage Leaves." Arthur John 

 Daish. Biochemical Journal, 1916. 10, 49-55- 



The crushed pulp of all the leaves examined {Tropceolum, potato, 

 dahlia, turnip, sunflower, and mangold) acts upon soluble starch or 

 gelatinised starch and forms reducing sugars ; of these the greater 

 part consists of glucose and the rest is maltose. It seems clear that 

 the pulp contains the enzyme maltase which acts on maltose, con- 

 verting it into glucose. By reason of the instability of maltase it is 

 necessary to avoid the use of heat or chloroform in preparing the pulp. 



XXIV. " The Distribution of Maltase in Plants." III. — " The 

 Presence of Alaltase in Germinated Barley," Arthur John 

 Daish. Biochemical Journal, 1916. 10, 56-76. 



Previous observers have shown that the action of malt extract on 

 starch gave rise to maltose, but not to glucose. It has, therefore, been 

 supposed that maltase is absent from barley. The author finds, 

 however, that the extract had usually either been treated with chloro- 

 form, or heated to 50-60°, by either of which treatments the maltase 

 is destroyed. By allowing the finely powdered germinated barley 

 grain to act on starch or maltose at 38° a large amount of glucose is 

 formed, and, as the proportion of glucose increases, that of maltose 

 falls. It seems evident that maltase is present and is acting on the 

 maltose. 



XXV. " The Use of Enzymes and Special Yeasts in Carbohydrate 



Analysis." W. A. Davis. Journal of the Society of 

 Chemical Industry, 1916. 35. 



The analytical methods elaborated by the author at Rothamsted 

 for the estimation of saccharose, raflinose, maltose, starch, and the 

 mixture of dextrose and laevulose are summarised. The necessary 

 working details are given. 



