One of the most remarkable exhibitions of plant force I ever saw was in
a Western city where I observed 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 irrepressible
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 cultivated 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 independent source
of energy, seems to me obvious enough, but that it does not manifest
energy, use energy, or "exert force," is far from obvious. If a growing
plant or tree does not exert force by reason of its growing, or by
virtue of a specific kind of activity among its particles, which we name
life, and which does not take place in a stone or in a bar of iron or in
dead timber, then how can we say that any mechanical device or explosive
compound exerts force? The steam-engine does not create force, neither
does the exploding dynamite, but these things exert force. We have to
think of the sum total of the force of the universe, as of matter
itself, as a constant factor, that can neither be increased nor
diminished. All activity, organic and inorganic, draws upon this force:
the plant and tree, as well as the engine and the explosive--the winds,
the tides, the animal, the vegetable alike. I can think of but one
force, but of any number of manifestations of force, and of two distinct