Here is a puzzle. Well maybe not so much a puzzle as a curiosity.

While vacationing in upper Michigan last week I walked six qnat-infested miles through the beech and fir northern woodlands to the sandy shores of Lake Superior to see this sight...

http://community.webshots.com/s/image1/4/3/38/95140338pgQRTn_fs.jpg

Standing forty-five feet tall above the shoreline of Lake Superior is Chapel Rock - a detached piece of resistant sandstone of a very aesthetically pleasing shape, and color, and size. Yet the circumstance of a single forty foot dark green fir tree growing incongruously from the stone flat at the top of the rock made for a symmetrical beauty too lofty for low-life modern men like me and might be best left for the delicate sensitivities of dead Indian gods.

Never-the-less we low-life men are a nosey sort, and like dull-witted engineers we make ourselves pedestrian by asking dull-witted questions like...

Seeing that the soil cover on Chapel Rock was only about an inch or so deep we are not surprised to see a ten inch in diameter root from the fir tree reach over a horizontal span of twenty feet of empty space to reach a larger soil covered rock at exactly the same elevation near-by.

Question: Most trees don't have eyes, so how did that tree know where the soil and water was?

Thin tendrils in all directions. When one hits soil, a feedback loop is created: nutrients => growth => greater ability to take up nutrients. Hence only that one will have grown. Less successful efforts will have withered away. Clinging vines and their tendrils/suckers show similar tendencies.

Just a guess, though.

Most trees don't have eyes

You obvious ain' never seen that Windex® ad on the TV.

Of course you are right, Shanks, but the question remains... How did the fir tree keep its big root stiff enough to horizontally span twenty feet of empty space?

(Thats it! Like a schoolboy in full rut I had to say it. Done! Enough silliness. Now back to the important question in hand)

And Faldage, you sneaky devil, you too are right. It can be said that plants and trees can see even better than humans. Seeing is perception and the only way for humans to perceive light is through chemical absorption. The same as plants, but different. It is our brain/eyes that outlines and distinguishes separate environmental entities.
Plants don't need these nice refinements to survive this cruel hungry world. Good thing too, they can't run.

I don't know about chemical eyes (almost said chemical plant eyes!) but I've noticed vine shoots, on the ground, growing directly toward the nearest tree.
Kinda scary.

In an email to me wwh came close to the answer to my question , so I'd best hurry my explanation of the air root conundrum so I'll get credit for being hip and in the know. Which is...

The largest and deepest (over 1200 feet) of the Great Lakes is rising on the western side. The land is still rebounding from the depressed state it underwent during the last glacial period which ended 12,000 years ago when it was depressed by the weight of several thousand vertical feet of ice. Today the land is rising at the rate of one to four feet per century.

Meanwhile the land to the south and east has achieved an equilibrium of sorts and no longer rises. The effect, in effect, is like tilting a great pan of water and so Lake Superior is slowly draining into the other great Lakes.

This unassailable reality plays havoc with Lake Superior's shorelines and erosion rates multiply, and inadvertantly this was the penultimate cause of the air root of the fir tree of Chapel Rock. To wit...

Sometime during the last 100 years a great thousand ton sandstone rock was removed from beneath the twenty foot tree root by great storm waves and today that rock is sand on the nearby beach.

(wwh had proposed that a commercial sand company had removed the sand supporting the root by strip mining as they have in other parts of Michigan where their dune mining is evidenced by vast and unsightly open pits.)