HOW CROPS GROW. 



decomposition, (Hoffmann, Quart. Jour. dhem. Soc., jx 

 767.) A kind of gum also appears in solutions of cane- 

 sugar or in beet-juice, when they ferment under certain 

 conditions. Inulin and the gums yield sugar, (levulose,) 

 but no dextrin, when boiled with weak acids. 



d. It will be noticed that while physical and chemical 

 agencies produce these metamorphoses in one direction, it 

 is only under the influence of life that they can be accom 

 plished in the reverse manner. 



In the laboratory we can only reduce from a ^higher, 

 organized, or more complex constitution to a lower and 

 simpler one. In the vegetable, however, all these changes, 

 and many more, take place with the greatest facility. ( ^ . 



The Chemical Composition of the Uellufose Group. 

 It is a remarkable fact that all the substances just de 

 scribed stand very closely related to each other in chemical 

 composition, while several of them are identical in this 

 respect. In the following table their composition is ex 

 pressed in formula. 



CHEMICAL FORMULAE OF THE BODIES OP THE CELLULOSE GROUP. 



Cellulose 

 Starch 

 Inulir 

 Dextnii 

 Bassorin 

 Veg. Mucilago 

 Metarabic acid 

 Arabic acid 



C 13 H ao O ig 



Ara1 lc 13 H aa O n 



Cane sugar 



Fruit sugar I n TT r* 



Grape sugar [ C H &amp;gt; 



It will be observed that all these bodies contain 12 

 atoms of carbon, united to as much hydrogen and oxygen 

 as form 10, 11, or 12 molecules of water. We can, there 

 fore, conceive of their conversion one into another, with 

 no further change in chemical composition in any 

 than the loss or gain of a few molecules of water. 



