But how does it build itself?  Myriads of rootlets search the surrounding country for elements it needs for making bark, wood, leaf, flower, and seed.  They often find what they want in other organizations or other chemical compounds.  But with a power of analytical chemistry they separate what they want and appropriate it to their majestic growths.  But how is material conveyed from rootlet to veinlet of leaf hundreds of feet away?  The great tree is more full of channels of communication than Venice or Stockholm is of canals, and it is along these watery ways of commerce that the material is conveyed.  These channels are a succession of cells that act like locks, set for the perpendicular elevation of the freight.  The tiny boats run day and night in the season, and though it is dark within, and though there are a thousand piers, no freight that starts underground for a leaf is ever landed on the way for bark or woody fiber.  Freight never goes astray, nor are express packages miscarried.  What starts for bark, leaf, fiber, seed, is deposited as bark, leaf, fiber, seed, and nothing else.  There are hundreds of miles of canals, but every boat knows where to land its unmarked freight.  Curious as is this work underground, that in the upper air is more so.  The tree builds most of its solid substance from the mobile and tenuous air.  Trees are largely condensed air.  By the magic chemistry of the sunshine and vegetable life the tree breathes through its myriad leaves and extracts carbon to be built into wood.  Had we the same power to extract fuel from the air we need not dig for coal.

In doing this work the power of life in the tree has to overcome many other kinds of force.  There is the power of cohesion.  How it holds the particles of stone or iron together!  You can hardly break its force with a great sledge.  But the power of life in the tree, or even grass, must master the power of cohesion and take out of the disintegrating rock what it wants.  So it must overcome the power of chemical affinity in water and air.  The substances it wants are in other combinations, the power of which must be overcome.

Gravitation is a great power, but the thousand tons of this tree’s vast weight must be lifted and sustained in defiance of it.  So for a thousand years gravitation sees the tree rise higher and higher, till the great lesson is taught that it is a weakling compared with the power of life.  There is not a place where one can put his finger that there are not a dozen forces in full play, every one of which is plastic, elastic, and ready to yield to any force that is higher.  So the tree stands, not mere lumber and cordwood, or an obstacle to be gotten rid of by fire, but an embodiment of life unexhausted for a thousand years.  The fairy-fingered breeze plays through its myriad harp strings.  It makes wide miles of air aromatic.  Animal life feeds on the quintessence of life in its seeds.  But most of all it is an object lesson that power triumphs over lesser power, and that the highest power has dominion over all other power.