If you let your brain lie idle, and allow your teacher or your book to do for you not only all the asking of questions, but also all the thinking-out of answers, it will get as dull and rusty and good for nothing as a machine that is laid by for a long time gets dull and rusty and good for nothing.
I should be sorry to think that any of you children were carrying about in your heads any such rusty, good-for-nothing brains. So if you wish to keep them bright and clean, and in good working order, you must try to do your own thinking.
And now, hoping you have tried to guess for yourselves the reason of this crooked back, I will explain it to you.
But first handle carefully the tip of one of the upper leaves on the larger bean plant. You see how delicate this is.
Then feel how firm and hard and tough is the green hoop of the plant which is just breaking through the earth.
Now suppose the bean plant had grown straight up into the air, would not its uppermost part have been the delicate leaf tips?
Can you not see that these would have been too frail to work their way uninjured through the earth?
But by crooking its stout stem the plant opened quite easily a path for itself and for its leaves, and no harm was done anywhere (Figs. [106], [107]). Was not this a clever thought? But really every step in the life of the plant is full of interest, if we watch it with sharp eyes and a brain in good order.
Part III—Roots and Stems
