Compound Celluloses 185 



the cold ; from the solution the * gum ' is precipitated on the 

 addition of alcohol. The yield varies from 10-20 p.ct. of the 

 weight of the wood. The gum is easily hydrolysed by boiling 

 dilute acids with formation of xylose. Jute, on the other hand, 

 gives only very small yields of this product, Tollens obtaining 

 only 1 75 p.ct. by digesting the fibre with 5 p.ct. NaOH solution. 

 This product also yields xylose on hydrolysis. 



It is this difference of yield of the proximate product which 

 requires to be emphasised, as it is altogether out of proportion 

 to the relative yields of furfural. With the progress of 

 lignification, in fact, there is probably a progressive formation 

 of pentosan resulting from molecular changes within the 

 particular group. These pentosans differ from the parent sub- 

 stance or complex in readily yielding to hydrolysis, and to 

 this extent may be regarded as dissociated or split off from 

 the fundamental tissue-substance in other words, as excreta 

 or end-products of metabolism. This view necessarily is in- 

 volved in the wider question of the physiological significance 

 of the furfural-yielding constituents of plants. De Chalmot 

 has published a series of communications in elucidation of 

 this question, under the titles * Soluble Pentoses in Plants/ 

 * Pentosans in Plants, '&c. (Amer. Chem. Journ. 15, 16). One 

 important result of these investigations is the conclusion that 

 pentosans are not formed in any perceptible quantity by the 

 assimilation process. This is equivalent to the statement that 

 they must arise by secondary transformations of the hexoses 

 before or after their elaboration into the permanent tissue of 

 the plant. 



Investigations, of the germination process in relation to 

 pentosans have given variable results : in some cases there is 

 an increase in the total pentosan, in others a decrease ; and in 

 certain cases the pentosans of the seeds, e.g. of Tropaolum 

 ma/us, appear to behave as ' reserve materials.' The authors 



