1884.] of the cell-wall and middle lamella. 93 



at any rate, regard them with suspicion, recognizing as we do the 

 great difficulties connected with the isolation of pure substances, 

 and consequently the little that is absolutely known of their 

 chemical properties and constitution. This is perhaps especially 

 true of the various bodies produced by the mucilaginous degenera- 

 tion of cellulose. 



It maybe very justly observed that great light has been thrown 

 on the constitution of the cell-wall, in consequence of two com- 

 munications which have recently appeared in the "Annates de 

 Sciences Naturelles" the one by Fremy 1 , and the other by Fre*my 

 and Terreil 2 . By a careful and patient study of the chemistry of 

 tissues, the well-known investigator who had so long ago isolated 

 cutin 3 , has now succeeded, not only in confirming his previous 

 researches, but also in extending them, in such a manner, as to 

 make a very decided and important advance in the field of 

 Botanical Microchemistry. 



The following is the classification adopted by the authors. 

 Having it must be premised (though not definitely stated in their 

 paper) separated the foreign substances occurring as cell-con- 

 tents, &c. by some such method as successive treatment with 

 petroleum spirit, alcohol, ether, and water, they arrange the 

 various constituents of vegetable tissue under seven heads, e.g. 

 (1) Cellulose substances, (2) Vasculose (Lignin), (3) Cutose, 

 (4) Pectose, (5) Calcium Pectate, (6) Nitrogenous substances, 

 (7) Mineral substances. 



The cellulose substances include all those bodies which dissolve 

 without colouration in bihydrated sulphuric acid (H 2 S0 4 , 2H 2 0) 

 producing dextrin and sugar, and which resist the action of alkalies 

 and oxidising agents. By means of Schweitzer's reagent (am- 

 monio-sulphate of copper) three well-defined varieties may be 

 separated. 



{1. Cellulose proper. Easily soluble in Schweitzer's reagent. 

 2. Paracellulose. Soluble only after the action of acids. 

 3. Metacettulose. Insoluble even after preliminary action of acids. 



Vasculose (Lignin) 4 . Insoluble in bihydrated sulphuric acid or 



1 Fre"niy, Ann. des Sci. Nat. 6th ser. xin. 1882. 



2 Fremy et Terreil, reference as before. 



3 Fremy, Ann. des Sci. Nat. 4 ser. xn. p. 331. 



4 Max Singer (Sitzb. d. k. Akad. in Wien, lxxxv. 1882) finds that after very 

 lengthy treatment (e.g. 6 weeks) with water which was allowed to boil for 10 hours 

 a day, the following substances may be extracted from lignified tissue, viz. (1) 

 Vanillin, (2) Coniferin, (3) a certain quantity of gum, (4) the wood gum of Thom- 

 sen, (5) a substance coloured yellow by hydrochloric acid. From these results he 

 is inclined to believe that the so-called lignin is in reality a mixture of many 

 substances. It is not however apparent that by his methods he has actually 

 extracted the lignin from the tissue. One would rather imagine the substances 

 dissolved by boiling water were bodies which occur in lignified tissue. Thus on 



