354 Carhohiidnitca of the Leaf of the Potato 



large a quantity of substance as possible 1 litre of the 2)urifiefl aqueous 

 solution of the sugars (a quantity which represented 44-09 grms. of the 

 total vacuum-dried leaf matter) was evaporated in vacuo to 175 cc. 

 and made up to 250 cc. Three portions of 50 cc. each were fermented 

 during 3 weeks to 1 month with *S'. marxianus and S. exiguus, and after 

 treatment with alumina cream made up to 100 cc. Two dupUcate 

 fermentations were carried out with a pure culture of distillery yeast. 



50 cc. of the filtrate (representing 4-469 grms. of t.v.d.m.) gave in 

 the case of the S. marxianus and S. exigwis, 0-0524 grm. CuO ; and 

 gave in the case of the distillery yeast, 0-0500 grm. CuO. 



These values are pnictically identical and well within the range of 

 error of the method. They show that maltose was entirely absent from 

 the turnip leaf in question. The reducing power, as pointed out [1914], 

 is to be attributed to unfermentable pentoses ; it corresponds with 

 0-51 per cent, of pentose; 0-60 per cent, was found by the ordinary 

 phloroglucinol method when applied directly to the solution containing 

 the sugars, prior to fermentation. 



Brown and Morris, in their important memoir, gave what was 

 undoubtedh' good evidence of the presence of maltose in their extracts 

 of Tropfwlum leaf. They were not content merely with the analytical 

 data but endeavoured "'in view of the immense importance which must 

 necessarily be attached to this product of starch hydrolysis to obtain 

 more direct evidence of its presence." They succeeded in isolating an 

 osazone, apparently identical with maltosazone, from the solution of 

 the mixed sugars contained in a large quantity of the dry leaves of 

 Tropceolum, and analysed it. Finally they showed the presence of 

 maltose by treating a solution of the mixed sugars of the leaf, after 

 completely inverting the saccharose, with a preparation of the enzyme 

 maltase. This enzyme always brought about a large increase in the 

 cupric reducing power, amounting generally to about 75 per cent, of 

 the increase observed on digesting the same solution with dilute acid. 



It is impossible in view of these facts to doubt that maltose was 

 present in the material woi-ked with by Brown and Morris. It is, 

 however, possible to reconcile these results with our own by taking 

 into account the difference between the methods of extraction of the 

 sugars adopted by Brown and Morris and by ourselves. We have been 

 led to conclude that plant leaves which store starch contain in addition 

 to the enzymes of ordinary diastase (a fact which was first definitely 

 proved by Brown and Morris) the enzyme maltase, which is capable of 

 breaking down maltose to dextrose. We have shown in a previous paper 



