VEGETABLE ACTION. 191 



and passively, where it is the most minute. The un- 

 germinated seed may pass through many vicissitudes 

 which would kill the plant even in the early stages of 

 of its development ; and the power with which the 

 awakened germ can add to its bulk, when young 

 and small, is much greater than when it approaches 

 maturity. 



In many of these phenomena which we can observe 

 because they belong to matter, or are such as can be 

 changed only by a change in that, we find that the 

 energy increases according to some fixed and definite 

 law, in proportion as the distance is diminished.- In 

 the cases of gravitation and light, as it is the section 

 of the body that is acted upon, and as that section is 

 a surface, we find that the intensity of the action 

 varies with the apparent extent of the surface as seen 

 at the different distances, that is, inversely as the 

 squares of these. No geometer has yet ventured to 

 give us a formula for the diminution of vegetable 

 action as the space over which it is exerted is in- 

 creased ; or attempted to investigate the laws according 

 to which the plants have their varied durations, or 

 their degrees of seasonal change; and yet these are 

 all matters of the most legitimate philosophy. Why 

 should we not know to what organization it is that 



o 



the mushroom lasts for days, the mignionette for 

 months, the elm for years, and the cedar for ages ? 

 A grain of mustard seed and a grain of turnip seed 

 are very like each other, and the plants are so much 

 allied that if they be sown promiscuously in a 

 field, in such a manner as to perfect their flowers at 

 the same time, they will so much affect each other, 



