Compound Celluloses 181 



tissue, the products of modification remaining associated with 

 the residues of the parent substance in a state of combination 

 or of intimate mixture, the final products of metabolism 

 (aromatic products, pentosans, &c.) being excreted and taking 

 no further part in the organic processes of the tissue. 



We pass now from general deductions as to the con- 

 stitution of the woods to the consideration of the results 

 of special investigations (a) of particular constituents or 

 reactions of the woods as a class ; (b) of particular woods. 



(a) With the advance of analytical methods, characteristic 

 constituents of the woods may now be determined with pre- 

 cision. Estimations of furfural and methoxyl have been carried 

 out in extended series, and the results are significant for their 

 uniformity on the one hand, and for the indications of pro- 

 gressive variation with the progress of lignification on the 

 other. 



(i) ESTIMATIONS OF FURFURAL. Furfural-yielding consti- 

 tuents. In a recent publication of Professor Tollens (Zeitschr. 

 Ver. f. d. Riibenzucker Industrie, 44, No. 460) he gives a resume 

 of results obtained by himself and others who have collaborated 

 with him in the investigation of the furfural-yielding con- 

 stituents of plant tissues. The following numbers have been 

 selected as the mean results for the more important woods : 



De Chalmot has made a more extended series of deter- 

 minations (Amer. Chem. Journ. 16, 224), the results of which 

 are given in the table on p. 182. 



There is therefore a striking uniformity amongst the woods 



