34 THE THEOKY OF IONS 



absorbed by the roots are dissociated into ions which 

 are united in the chloroplastid to form a carbohy- 

 drate molecule, thus : C0 2 + H 2 = CH 2 + 2 . This 

 is the first stage in the formation of starch and sugar, 

 and it is never performed except by plants containing 

 chlorophyll and in the presence of potash salts. 

 Potassium takes no direct part in the process, but it 

 has a well-marked, indirect effect, and the process 

 is a more intricate one than is indicated by the 

 equation. CH 2 may be formed by a combination 

 of CO and H ions ; but peroxide of hydrogen is pro- 

 duced from water by the sun's rays, therefore 

 hydroxyl or OH ions may take a part in the process. 

 Such constructive work cannot be done without 

 energy ; and the plant avails itself of the kinetic 

 energy of the sun's rays, which is the force dis- 

 sociating C0 2 and H 2 into ions. Plants without 

 light -and protoplasm without chlorophyll are unable 

 to construct starch or sugar from these materials ; 

 and animals or parts of plants which do not contain 

 chlorophyll must derive their carbon for constructive 

 purposes from more complex compounds or already 

 organised material. Out of the simple plastic 

 molecule containing C, H, and more complex 

 substances are formed by polymerisation and con- 

 densation of the simple molecules ; and the process 

 by which these compounds are united is a complex 

 one, which results in the formation of starch, sugar, 

 cellulose or fat. 



Starch is an insoluble material which is formed in 

 the leaves of plants and deposited therein. When 

 it is carried from place to place for nutrition, growth 

 or storage, it is converted under the influence of an 



