  A whole week went by before Uncle George was ready for the next lesson. At last he called the children and said to them—“Tom, will you please fetch me the seeds which we put on the wet blotting-paper under the tumbler? Frank, bring me two leafy branches from a rose-bush in the garden; and, Dolly, please fetch two glasses from the kitchen.” Now there was nothing the children liked better than to help their Uncle George, and all three rushed off at once to do his bidding. While they were away Uncle George himself Sun-flower Plant in Water. “Now, children,” said Uncle George, “we are ready to begin our lesson. Fill one of the glasses with water, Frank, and put one of your leafy rose branches in each glass—one branch in water and the other in a dry glass. Can you tell me what will happen to the branches?” The children had many times seen what had happened to flowers when the maid had forgotten to put water in the vases, so that Tom readily said, “Yes, the one in the dry glass will wither, while the one in the water will keep fresh for some time.” “How do you know that?” “Because it always happens, Uncle,” said Frank. “Why, sometimes the flowers we gather in the wood are faded before we get home. They often come back to life when put in water.” “You are quite right, Frank,” Uncle The Sun-flower, faded. “That plants require water,” said Tom. “That whenever you cut off their water supply they die.” “Quite right, Tom. We shall see by and by that plants are always giving off a great deal of water to the air from their leaves. “It must be from the soil,” said Frank. “It must be,” said Uncle George. “If we keep a plant in a pot without watering it, it soon dies. All the water it contains will by and by travel up to the leaves. It passes out through tiny pores in the leaves into the air. If no more water comes up from the soil, the plant withers and dies. The roots of plants search the soil in all directions for “If we boil away some water from the tap, we shall find some solid matter left behind in the dish. Thus we see that in order to get a small quantity of food, plants take up a great quantity of water from the soil. Most of the water is sent into the air from the leaves. But the food stuff remains in the plant, just as it did in the dish. “Now I am going to show you how this water gets into the plant. Look at these little seeds on the damp blotting-paper! “Each seed has a small plant with a long root, and small, stout green leaves. Look at the roots and tell me what you see?” “They are covered with silky stuff,” said Frank. “Yes. Now take this glass, which will make things look bigger than they really are, and look at the roots once more.” “The silky stuff is a number of fine hairs,” said Frank. THE OTTER FIELD-MICE “That is quite right, Frank,” said Uncle George. “These are the root-hairs. Each of these hairs is a long bag or sac, of very thin skin. It is filled with a liquid called sap, which is slightly denser, or heavier, than the water in the blotting-paper. Now, do you see how a plant takes food from the soil, when it is growing in the garden or in a field?” “Yes, I think I do,” said Frank. “The water in the soil contains very little plant-food. The water inside the tiny sac contains very much.” “And what have you to say, Tom?” “One of these liquids is denser than the other,” said Tom. “Both are separated by a thin skin. The lighter liquid outside the sac will pass into it quickly, while the heavier liquid will pass out slowly.” “Bravo! Tom!” said Uncle George. “I couldn’t have given a better reply myself. The water from the soil passes in quickly. The sap from the inside of each root-hair passes out slowly. If they were both of the same density, neither would pass through the skin. If the water in the soil were the denser, then the sap would pass out so quickly that the plant would soon be robbed of its water. “Here are two young plants, each growing Tom did as he was asked. Plants watered with Fresh and Salt Water. “See,” said Uncle George, “the one which you watered with brine is drooping. It is bending over the pot. That is because the water outside its root-hairs is denser than that which is inside the plant.” “How does the water get up from the roots to the leaves?” Frank asked. “Just in the same way as the oil travels up the wick of the lamp. Water will always travel up through small spaces.” Uncle George poured some red ink into a saucer, and dipped the corner of a lump of sugar into it. The red ink ran up into the sugar until it was red all over. Next he took a bundle of very small glass tubes, and dipped the ends of them in the ink. The ink ran up the tubes, filling them to the top. “Inside every plant,” Uncle George went on, “there are thousands of long tiny tubes, up which the water travels. In fact the veins of a leaf are just bundles of tubes, something like the bundle I hold in my hand.” Questions and Exercises.
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