100 ORIGIN AND NATURE OF LIFE 



had to surge a long way up from the depths 

 before a green plant cell came into being. 

 Once such a cell was formed it would retain 

 its stability under suitable environment, and 

 form a new point of departure, but there 

 exists a wide hiatus between inorganic mole- 

 cules and the green plant cell which we must 

 bridge as best we may before we begin to 

 understand the origin of life. 



The present is, however, the place to 

 describe briefly that peculiar property pos- 

 sessed by the carbon atom of uniting with its 

 fellow atoms, which is there ready to yield 

 material for the physico-chemical structures 

 of life so soon as the energy transformer has 

 been evolved. In later chapters, the interval 

 will be dealt with lying between inorganic 

 molecules and the green plant cell and its 

 organic products. 



It is only a chemical atom possessing a high 

 valency which is capable of uniting in this 

 way so as to form a very large molecule, apart 

 from the quite different mode of formation 

 of bodies called colloids to be dealt with in 

 the next chapter. Colloids, it will be found, 

 are formed by molecular unions in which each 

 molecule behaves as a single atom, just as 

 previously in forming the atoms the electrons 

 united. In the colloid, each constituent 



