74 READINGS IN BIOLOGICAL SCIENCE 



going. You grow breathless. Well, this is the best that giants can do in 

 such cramped space. We must give up while still three hundred yards 

 from where cells actually come to grips with the soil. We are at the edge 

 of a zone of a rootlet called its "gro\\'ing point," where cells are being 

 multiplied so fast that the tissue is warmed by their energy; the place is 

 a fountain of new cells which appear to press forward like a determined 

 rabble. But all is orderly. Each of the tens of thousands of individuals knows 

 how to place itself and what to do. If you stayed here a week you would 

 find that the rabble had shaped itself into rows of ducts, and fibers of 

 wood and bark, extending the Hues that we have followed through branches 

 and trunk and roots. This growing point is always extending the structure 

 of the root and pressing forward upon the tip, forcing it onward through 

 the soil. 



Will you stop here and listen to some prosy words about the operations 

 in the tip, or will you now consent to be made small, so that you may see 

 something for yourself? Science can not reduce your size a great deal 

 more. Just let yourself be minimized to a tenth of your present stature, 

 till you are one thirty-thousandth of an inch tall, like one of the smallest 

 bacteria — that is all that is required. 



While you were recovering from the vertigo of the operation I have 

 been carrying you back through the rootlet and out into one of the fine 

 hairs that grow from it. The cells here are actually smaller than those which 

 we saw in the needle, but to you, in your present state, they show a diam- 

 eter of one hundred twenty-five feet. Finding a passage between them 

 is possible, but difficult. We must take our time, looking for favorable 

 places where we can pry cells apart far enough to make way for our 

 bodies. Gradually, but sliding here and shouldering there, we pass a cell, 

 then a second, finally a seventh. We are at the outpost of a tree. 



The outer surface of this outermost cell is wrestling with a bit of loam 

 that is compressed between a huge slab of mica and a boulder of quartz. 

 The loam is in possession of some molecules of water. It grasps them greed- 

 ily and tries to defend them. The wall of the cell presses close, squeezing 

 between the loam and its protecting slab and boulder, slowly gathering 

 the loam in its embrace, drawing the filmy bits of water by some attraction 

 that physics can not investigate. Slowly, relentlessly, powerfully the cell 

 continues its depredation. The loam is sucked dry. The cell gathers to- 

 gether its booty of moisture, conveys it to the inner side of itself, and pushes 

 it against the outer wall of the next cell. This receives the water and trans- 

 fers it to a third cell. The water is passed thus from "hand to hand," through 

 the hair, into a fibrous root, and on to a narrow tunnel like the one which 

 conveyed us down from the needle. The water is mingled with other drop- 

 lets in a stream which flows on, parallel to the sap-duct, on for a hundred 

 miles, on for a thousand miles, on and on till it is delivered to a needle and 

 used in a sugar-making disk. 



