AMYLASE IN THE LIVING CELL 125 



The total 144 c.c. of solution or ten grams of leaf have 

 therefore yielded : — 



Maltose 0-5688 grm. = 0-5486 grm. starch 

 Dextrin 0-0922 grm. = 0'0922 „ 



Total = 0-6408 „ 



Ten grams of leaf therefore contain 0-6408 grm. starch or 

 6-466 per cent, of their weight. 



I If an appreciable amount of malt extract has been used, a 

 correction must of course be made for it by determining its 

 optical activity and copper-oxide reducing power in a similar 

 manner. 



The determination of the actual amount of amylase 

 present is not possible, but comparative determinations can 

 be made by measuring the amount of saccharification which a 

 given amount of tissue can perform under standard conditions 

 in a given time. The starch, it must be remembered, in order 

 that the ' law of proportionahty ' may obtain, must always 

 be in large excess. 



Brown and Morris investigated thirty-four species of 

 plants ; they found that aU of them contained a measurable 

 amount of amylase, the greatest quantities being obtained 

 from leguminosae, especially the common pea. They found 

 that the amount of amylase present varied with the environ- 

 ment, the greatest quantity being found when the plant was 

 kept in darkness ; on exposure to hght diminution in the 

 quantity of amylase present took place. It is, of course, 

 well known that starch formation in the leaf cells takes place 

 in presence of light ; it appears, therefore, that the digestion 

 of the starch and consequent formation of amylase takes 

 place in darkness ; thus the starch and amylase are present 

 in inverse proportion. 



