164 Cellulose 



investigated by Tollens in regard to its more characteristic 

 groups, the researches being chiefly directed to the furfural- 

 yielding groups. What we have to emphasise is the recognition 

 by Tollens that in this tissue-substance the various groups are so 

 united as to constitute a homogeneous complex. This tissue 

 has the closest resemblance to the grain-bearing straws^ which 

 have been recently investigated by C. Smith and the authors 

 (J. Chem. Soc. 1894, 472 ; Berl. Ber. 1894, 1061). 



The starting-point of these researches was the observation, 

 already noted (p. 84), that the celluloses, isolated from their 

 stem tissues, themselves give a large yield of furfural when 

 boiled with hydrochloric acid ; at the same time none of the re- 

 actions of the pentaglucoses. It appears from these researches, 

 and from subsequent results, that from germination, continu- 

 ously with the growth of the stem, there is a steady increase in 

 the proportion of furfural-yielding constituents, and that these 

 are mainly utilised in building up the permanent tissue of the 

 stem. These results are noted paripassu with lignification, and 

 they further generalise the chemical features of the process 

 which were brought out in connection with the jute fibre viz. 



(1) the cellulose of a lignified tissue is, when isolated, found 

 to be invariably an oxidised and furfural-yielding cellulose ; 



(2) in the non-cellulose, pentosan groups are present in associa- 

 tion with an easily hydrolysable oxycellulose, and with unsatu- 

 rated or keto R. hexene groups. 



As lignocelluloses, the straws are generally differentiated from 

 the typical lignocellulose, (i) by their structural complexity ; 

 (2) by their lower carbon and proportionately greater oxygen 

 percentage ; (3) by the relative susceptibility of the non-cellu- 

 lose to hydrolysis ; (4) by the much lower percentage of cellu- 

 lose and the composition of this cellulose. 



As a consequence of these differences, the straws are more 

 easily attacked by the thiocarbonate treatment. The following 



