Compound Celluloses 173 



purely hydrolytic treatments, however, they may be varied, both 

 as to reagents and conditions of action. 



Similar results are noticed with oxidising agents. Thus 

 chromic acid solution (20 p.ct.) attacks the parenchymatous 

 tissue of young growths much more rapidly than the vessels, 

 which, with a careful regulation of the treatment, may by its 

 means be isolated more or less perfectly. In the woods the 

 reagent appears to attack the vessels more rapidly than the 

 wood cells and medullary tissue ; but any difference of action 

 is not such as to permit of an isolation of the one or other 

 group. 



Schulze's reagent (HNO 3 and KC1O 3 ) also attacks the 

 several groups more or less uniformly, the differences noted 

 being rather as between woods of different ages and species ; 

 thus sap wood is more resistant than heart wood, and the ' soft ' 

 than the ' hard ' woods. 



In view of these results, the methods of classification 

 adopted by Fremy will be seen to rest upon very insecure 

 foundations. The basis of the classification is the resolution 

 of the substance by successive treatment with HC1 (dilute and 

 cone.), H 2 SO 4 .H 2 O, cuprammonium, alkaline hydrates, &c. 

 Thus the following individuals have been isolated and defined 

 as follows : cellulose, paracellulose (soluble in cuprammonium 

 after treatment with acids), metacellulose (insoluble in cupram- 

 monium) and vasculose (Fre'my, Compt. Rend. 48, 862 ; 

 Urbain, Ann. Agron. 9, 529). This classification has been 

 severely criticised by Kabsch (Pringsheim, Jahrb. f. Wiss. Bot. 

 3, 357), and is entirely rejected by Sachsse (foe. cit.\ Hugo 

 Miiller (Pflanzenfaser, p. 7), and other authorities ; and it is 

 unnecessary to add anything to the criticisms of these writers. 



There have been many attempts to resolve the woods into 

 proximate constituents, but the authors have for the most part 

 concluded, from their investigations, (i) that the fundamenta 1 



