21 



These data show that more than half of the material dissolved from 

 the nodes and internodal fiber consists of reducing sugars, while in the 

 case of the pith, less than half of the soluble matter belongs to that 

 category. 



After heating the various samples with an alkali, the residues, after 

 washing with water, and acetic acid and water, were digested with dilute 

 sulphuric acid and the reducing sugars in the products ascertained. 

 The following results were obtained: 



Results for reducing sugars. 



The difference in the nature of the bodies dissolved by acid and 

 alkali are brought out in a striking manner by the above data. The 

 actual quantity of material dissolved by alkali is considerably greater 

 than is removed by an acid in the nodes and shells and only slightly 

 less in the pith. The bodies removed by alkali, however, contain 

 only a little more than half the quantity of reducing sugar found 

 in the matter removed by acids. For instance, it is known that xylan 

 is quite soluble in an alkali. It is also soluble in an acid, being con- 

 verted by the latter into xylose. The alkali, however, dissolves a large 

 quantity of material which sulphuric acid does not convert into reduc- 

 ing sugars. In the nodes, sulphuric acid dissolves 44.28 per cent of mat- 

 ter which has a reducing power equivalent to 28.86 per cent of dextrose. 

 In the same material, caustic soda dissolves 51.45 per cent of matters 

 which have a reducing power equal to 13.89 per cent of dextrose. It 

 is not convenient to directly convert the alkali extract into reducing 

 sugars by hydrolysis with sulphuric acid, because of the large quantity 

 of sodium sulphate which would be present. The approximate amount 

 is therefore obtained by the indirect method given above. 



SUCCESSIVE DIGESTION WITH ACID AND ALKALI. 



The total quantity of matter dissolved by successive treatments of 

 the samples at 3J atmospheres with 1/.25 per cent sulphuric acid and 

 1 per cent caustic soda solution is shown in the following tabular 

 statement : 



Solubility in acid and alkali. 



