247. COMPOSITION OF WOODY TISSUE. 253 



stance. The first is said to be the only one capable of resisting 

 the action of chlorine- water ; it can be isolated by the method 

 detailed in 116. The authors overlook the fact that several 

 units per cent, of a substance probably isomeric with cellulose 

 (? intercellular substance), removable by chlorate of potash and 

 nitric acid, are left associated with the cellulose. 



The cuticular substance alone is said to be insoluble in a mixture 

 of 1 eq. of sulphuric acid with 4 eq. of water ; it can be isolated 

 by treatment with acid of that strength, followed by washing with 

 pure water and dilute alkali. 



The incrustmg substances are estimated by difference. 



In a more recent publication, the authors observe that the 

 following are the principal substances they would expect to find 

 in tissue previously exhausted with indifferent solvents : 



Cellulose, soluble in ammonio-sulphate of copper. 



Paracellulose, insoluble in the same until after it has been acted 

 upon by acids. 



Metacellulose (fungin) insoluble in ammonio-sulphate of copper. 



All three modifications of cellulose are soluble in H 9 S0 4 , 2H 9 O. 

 (Compare also 248). 



Vasculose> insoluble in H 2 S0 4 , 2H 2 O, and in ammonio-sulphate 

 of copper ; soluble in alkalies only under increased pressure, and 

 decomposed by treatment with chlorine-water, followed by wash- 

 ing with dilute alkalies. 



Cutose, insoluble in H 2 S0 4 , 2H 2 O, and in ammonio-sulphate of 

 copper, but soluble in alkalies under the ordinary pressure. 



Pectose. convertible by acids into soluble pectin. 1 



I would observe that the substance designated as vasculose 

 (formerly called incrusting substance), agrees in the main with 

 my lignin ( 116). Lignin cannot, unfortunately, be separated 

 from cellulose without decomposition, and it is therefore impos- 

 sible to adduce direct proof that it does not consist of a mixture 

 of several chemical individuals. Nevertheless, I think it probable 

 that in some instances the cellulose is accompanied by a single 

 definite substance, 'lignin.' Stackmann 2 exhausted vegetable 

 substances rich in lignin with the indifferent solvents already 

 alluded to, as well as with dilute soda and dilute acid, and then 

 determined the approximate composition of the lignin by making 



1 Comptes rendus, Ixxxiii. 1136. (Journ. Chem. Soc. xxxi. 229). 



2 ' Studien uber die Zusammensetzung d. Holzes.' Diss. Dorpat, 1878. 



