THE BREATH OF LIFE 



Darwin measured the force of the downward 

 growth of the radicle, such as I have alluded to, as 

 one quarter of a pound, and its lateral pressure as 

 much greater. We know that the roots of trees in- 

 sert themselves into seams in the rocks, and force 

 the parts asunder. This force is measurable and is 

 often very great. Its seat seems to be in the soft, 

 milky substance called the cambium layer under 

 the bark. These minute cells when their force is 

 combined may become regular rock-splitters. 



One of the most remarkable exhibitions of plant 

 force I ever saw was in a Western city where I ob- 

 served a species of wild sunflower forcing its way 

 up through the asphalt pavement; the folded and 

 compressed leaves of the plant, like a man's fist, had 

 pushed against the hard but flexible concrete till it 

 had bulged up and then split, and let the irrepress- 

 ible plant through. The force exerted must have 

 been many pounds. I think it doubtful if the 

 strongest man could have pushed his fist through 

 such a resisting medium. If it was not life which 

 exerted this force, what was it? Life activities are a 

 kind of explosion, and the slow continued explosions 

 of this growing plant rent the pavement as surely as 

 powder would have done. It is doubtful if any cul- 

 tivated plant could have overcome such odds. It 

 required the force of the untamed hairy plant of the 

 plains to accomplish this feat. 



That life does not supply energy, that is, is not an 



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