X. THE CHEMICAL CONSTITUENTS OF PLANTS 193 



C 5 H 8 O 3V 



CH, 



which is probably O O 



COH.CHOH.CHOH.CH.CH 2 



These bodies are capable of fermentation with yeast, yielding 

 alcohol ; in this respect they differ from the pentoses, which are 

 apparently incapable of true alcoholic fermentation, though under 

 certain conditions they appear to be assimilated by the yeast plant 

 and to be destroyed. 



It is probable that the pure pentoses and pentosans are not digest- 

 ible (Ebstein), while these " furfuroid " bodies of the type just de- 

 scribed appear to be so. 1 From these results it seems that the plan 

 generally employed of determining the " total pentoses and pento- 

 sans " by distillation with dilute hydrochloric acid and precipitation 

 of the furfuraldehyde as osazone gives numbers which include these 

 furfuroid substances described above and which probably possess 

 greater value as food stuffs than the pentoses and pentosans. 



Lignose or Lignone (Gross and Bevan). Lignification is the con- 

 version of cellulose into woody fibre in the plant, a change which 

 greatly alters the physical properties of the materials. According to 

 Cross and Bevan, this change is accompanied by a chemical change 

 which may be empirically represented as loss of water 



2C 6 H 10 5 = C 12 H 18 9 + H 2 0. 

 Cellulose. Ligno-cellulose. 



The ligno-cellulose, however, is, like cellulose, a highly complex sub- 

 stance, and probably consists of a compound of cellulose proper with 

 lignone, an unsaturated substance containing ketone and aldehyde 

 groups. 



Ligno-cellulose therefore gives furfuraldehyde on treatment with 

 boiling hydrochloric acid and consequently probably contains either 

 pentosans or, more likely, furfuroids. 



The ligno-celluloses are probably partially digested by the herbi- 

 vora, and it is probable that the hippuric acid so characteristic of the 

 urine of these animals is derived from the digested ligno-cellulose of 

 their food. According to Cross and Bevan 2 the process of lignifica- 

 tion in a plant is characterised by the formation of groups of the 

 form 



XX 



C0<; j>CH 2 or C 6 H 8 5 



\/~t _ c* 



(OH), (OH), 



Sill 



our 

 2 Cellulose, 1895, p. 77. 



1 Cross, Bevan and Smith, Jour. Chem. Soc., 1897, Trans., 1003; also Cross, 

 Bevan and Kemington, Jour. Soc. Chem. Ind., 1900, 307. 



13 



