256 PLANT PHYSIOLOGY 



sented by the embryos in the seeds. The life cannot pass 

 over, however, without a physical basis; the substance of 

 the parent is given to and forms the offspring. The giving 

 of substance and of life are simultaneous if not identical. 

 When this gift exceeds a certain amount, the parent ceases 

 to be, it abandons its own body, it lives only in its off- 

 spring. Internal causes are what terminate the lives of 

 plants like these, but as we shall presently see (pp. 263- 

 76), these are profoundly affected by external influences. 



There are other internal causes which may terminate the 

 life of an individual. If its parent endow it so badly with 

 substance, form, or food that it cannot maintain the bal- 

 ance of constructive and destructive processes in which liv-' 

 ing consists, it will die. Its span of life is determined by its 

 own substance, structure, and energy, all of which, or the 

 means of gaining which, were given it by its parents. Such 

 an individual, unable to live long enough to produce off- 

 spring, ceases to live because its internal balance breaks. 

 Its life ceases because destructive processes exceed the con- 

 structive. Its lifeless substance thereupon becomes the 

 source of matter and of energy for living individuals of 

 other kinds. 



Since living may be said to consist in maintaining the 

 balance between construction and destruction, life may be 

 said to represent the balance of energy-storing and energy- 

 liberating processes. There is as much substance and as 

 much energy when there is no balance. When the balance is 

 attained, there is life; when the balance is not attained, 

 there is no life. When an individual dies without offspring, 

 there is less life in the world but no less substance or energy. 

 ■When an individual, having given sufl&cient substance in 

 .suitable form to its offspring to start them in their careers, 

 continues to live for a time, there is less life when it dies 

 but no less matter or energy. There is simply a different 

 .adjustment of forces, a different arrangement of matter. 

 But this different adjustment is merely local, more or less 

 individual. The population of a given locality may greatly 

 increase, but with the increase in number of human beings 

 there is a decrease in the number of living organisms of 



