86 Cellulose 



upon the starch granules themselves, to form the supply of nu- 

 trition to the embryo. In an exhaustive investigation of the 

 germination of the barley, Brown and Morris have thrown a 

 good deal of light upon this particular point, which they empha- 

 sise in the following words : * that the dissolution of the cell 

 wall invariably precedes that of the cell contents during the 

 breaking down of the endosperm is a fact of the highest physio- 

 logical importance, and one which for the most part has been 

 strangely overlooked.' 



A similar, but abnormal, dissolution of cell walls is that 

 which occurs in the attacks of parasitic organisms upon the 

 tissues which they invade. 



These processes are well known to physiologists, who, how- 

 ever, generally regard ' cell-wall ' and ' cellulose ' as substan- 

 tially identical terms. The chemical differentiation of the sub- 

 stances comprising cell walls is, on the other hand, an 

 entirely new field of research ; but although investigation 

 has not gone very far, the results are sufficient to show that 

 the celluloses of this order are enormously diversified. The 

 variations already disclosed are (i) those of the carbohydrates 

 yielded by ultimate hydrolysis, and (2) those of molecular con- 

 figuration or condensation. We have already seen that the 

 celluloses of the cotton group (a) yield dextrose as the ultimate 

 product of hydrolysis ; those of group (b) yield, in addition to 

 dextrose, mannose and probably other bodies ; and the group 

 we are at present discussing yield, in addition, galactose, and 

 the pentoses xylose and arabinose. In illustration we may cite 

 a few examples. Thus GALACTOSE has been obtained as a pro- 

 duct of hydrolysis of the cell walls of the seeds of Lupinus 

 luteus, Soja hispida, Coffea arabica, Pisum sativum, Cocos 

 nucifera, Phcenix dactylifera, &c. MANNOSE is obtained in 

 relatively large quantity from the * ivory nut,' and from a very 

 large number of other seeds ; and PENTOSES, from the seeds 



