CLASSIFICATION OF CELLULOSES 149 



CLASSIFICATION OF CELLULOSES. 



The naturally occurring celluloses may be divided into the 

 following groups : 



I. Typical or Normal Celluloses of the Cotton Type. 

 These are exemplified by the cellulose obtained from cotton, 

 flax, hemp, etc. 



II. Compound Celluloses of the Wood Cellulose, Jute and 

 Cereal Grass Types. The natural celluloses occurring in jute, 

 cereal straws, esparto grass, etc., consist of some form of 

 cellulose combined with a non-cellulose constituent, which may 

 be either of the nature of lignin in the case of lignocelluloses, 

 or a pectic or gummy substance in the case of pectocelluloses, 

 or a fatty substance in the case of adipocelluloses. This 

 group may therefore be subdivided into 



(a) Lignocelluloses, e.g. jute fibre. 



(b) Pectocelluloses, e.g. flax. 



(c) Adipo- or Cuto-celluloses, e.g. cork. 



III. Hemi-, Pseudo- or Reserve Celluloses. This is a some- 

 what heterogeneous collection of substances which differ 

 structurally from the fibrous celluloses, and occur in the cell 

 walls of the seeds of various plants ; such as Coffea arabica, 

 Sofa hispida, Lupinus luteus, Cocos nucifera, Tropceolum majus, 

 Impatiens balsamifera y Pceonia officznalis, and in peas and beans ; 

 celluloses of this type are much more easily hydrolysed than 

 other celluloses, and give rise to various sugars, such as mannose, 

 galactose and pentose. For this reason they may be regarded 

 as anhydrides of these sugars, and are therefore treated under 

 the heading of mannosanes (p. 137), galactosanes (p. 138), and 

 pentosanes (pp. 70, 143). 



In this group of celluloses are also included those which, 

 according to the researches of Brown and Morris, are dissolved 

 by the enzymes secreted by the germinating seed ; these are 

 sometimes referred to as reserve cellulose, though the name 

 seems ill-chosen, inasmuch as they would not appear always 

 to function as reserve material. 



One of the richest sources of cellulose in nature is the 

 cotton plant. The following table, taken from Bowman,* re- 

 presents approximately 'the composition of cotton fibre from 

 various sources. 



* Bowman : " The Structure of the Cotton Fibre," London, 1908, p. 147. 



