The Plant. 93 



Dextrine of commerce is a mixture of compounds varying in 

 complexity. Its gummy nature gives it value as an adhesive 

 paste. Stick-labels and postage stamps are coated with dextrine. 

 Mixtures of dextrines occur in the grains of cereal plants and 

 their amount increases at germination as a result of the decom- 

 position of starch. The relative proportions of chemical elements 

 in starch and the dextrines are the same, but the latter are ap- 

 parently simpler groups of a basal compound (C 6 H 10 5 ) r 

 ascending in complexity toward the composition of starch. Dex- 

 trines are precursors of the simple carbohydrate maltose, which 

 occurs in germinated grains. 



Galactans are complex poly-saccharides occurring particularly 

 in the seeds of leguminous plants, in some of which they are the 

 chief carbohydrates. In the process of hydrolysis, these com- 

 pounds combine with water to form the comparatively simple 

 hexose known as ' t galactose. " 



Cellulose, the basal constituent of woody fibre, is a poly-sac- 

 charide of great importance for its tenacity and rigidity, which 

 give form and resistence to the walls of mature plant cells. It 

 rarely occurs free in the plant, but rather as a constituent of 

 compound celluloses, such as the incrusting, lignified celluloses 

 or ligno-celluloses of cell walls. Cotton and hemp fibres are 

 single, elongated plant cells, whose walls are composed of nearly 

 pure cellulose. By treating these fibres successively with hot, 

 dilute acid, with hot, dilute alkali and finally with chlorine gas, 

 and washing out the products formed, the purest known cellulose 

 has been obtained. It is evident that to resist such treatment 

 this compound must be extremely stable. It can be brought into 

 solution, however, by certain reagents, and when treated with 

 strong sulphuric acid, followed by diluting with water and boil- 

 ing, it is broken down and partially converted to dextrose. 



This brief discussion of the properties of the various carbo- 

 hydrates in connection with their common products of decompo- 

 sition, may serve to indicate a common basis of structure for this 

 group of plant compounds. Thus, by the union of two mono- 



