Part 21 (1/2)
The roots, like all parts of the plant--like all parts of boys and girls and grown people, for the matter of that--are made up of little cells
Well, these cells, first on one side of the root and then the other, enlarge, and so pump in an extra flow of sap Now, as we know, the sap contains food for the plant, just as blood contains food for our bodies; and rowth So the side of the root where the cells first swell out grows fastest and thus pushes the root over on the opposite side Then the cells on this opposite side swell, and the root is turned in the other direction again So it goes--right and left, up and down And when these two ether, don't you see what you get? The round-and-round ht nohen you turned your finger round and round to imitate the motion of the root (I saw you!) The muscles that did the work swelled up first on one side and then on the other, just as they do when you bend your elbohen you walk, when you breathe, when you laugh
Andone set offire-wood, for example Yet you can play ball by the hour and never think of being tired until it's all over; because, for one thing, you are constantly bringing new o to bat, as you strike, as you run bases It's the same ith the roots, it seems For the theory is that after the cells on one side have swelled, they rest; then the cells on the other side get to work
”But what starts the s starts in my brain”
WHERE MR ROOT KEEPS HIS BRAINS
Just so again The root has a brain, too, or what answers for a brain
And the root's brain, is in its head; at least in the vicinity of its nose--that is to say, its tip It's the tip that first finds out which side of the road is best, and passes the word back to the part of the root just behind it to bend this way or that It's also the tip that feels the pull of gravity and knows that it's the business of roots to keep under cover And Mr Root just _will_ have it that way! You can't change his h he finally changed human people's minds a lot
[Illustration: WHERE MR ROOT WEARS HIS CAP
A root wears its cap right where you do--over its brain department; that is to say, the tip It is called the ”root cap” and protects the tip from injury]
This is how he tried it on a root He took a bean with a little root that had just started out into the world He cut off the tip and then set the bean so that the root stuck straight up It continued to grow that way for some little time Finally, however, a new tip had for up, as if the tip said to the rest of the root:
”Here, here, this will never do! Where are you going? You must bend _down_!”
Anyhow that's what the root proceeded to do One side seerew rapidly and so the bending was done
”Did you ever! But how does the tip send back word?”
”Don't ask me!” says the science man; say all the science men, even to this day ”We don't know yet just _how_ it's done But we're studying these things all the time, and we'll know more about it by and by
Meanwhile, perhaps you'll tell _us_ why you say 'ouch' and pull your finger ahen you touch so hot”
”Oh,” you reply, ”I say 'ouch' because it hurts; and teacher and the Physiology say my arm pulls my hand away because my head tells it to”
”Yes, but how does the head ? What's the connection?” says the science uess we'll have to tell him we don't knoon't we?
But all the root's brains aren't in the tip, any h our bodies, you know, are _little_ brains, the ganglia, that control different parts of the body
So it is with roots For instance, a root at a short distance from the tip, is sensitive to the touch of hard objects in such a way that it bends toward the away, as the tip does The result is that when a root coround, the sides of the root press close up to the sides of the pebble--turn around corners sharply, by the shortest route--and so get over the obstruction as soon as possible and resume their course in the soil
[Illustration: BUT THEY COULDN'T CHANGE ITS MIND
Sos were attached to a disk like that, and when the roots started to gron, the disk was turned to make theroard They turned doard Every time!]
And different parts of a plant's root systeravity, and some don't respond at all The tap-root, for exa out frorow any other way, and yet this is also supposed to be due to the influence of gravity Then, frorow out a third set, and they don't seerow out in all directions--every which way--so that if there is a bit to eat anywhere in the neighborhood they are reasonably sure to find it You see it works out all right
When a plant first begins to peep into the world out of that wonder box we call the seed, it's the root, as we know, that does the peeping; it coet a firrow right and left and all around and take a firrip There is an acid in the root that dissolves whatever the root touches that has any food in it--including pebbles and old bones--and so makes a kind of sticky stuff that hardens In this way these fibrous roots not only get good meals for themselves and the rest of the plant, but they hold the plant firive the tap-root soainst, as it were, while it pushes down for water, for the moisture in the damper portion of the soil beneath