“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 George replied. “See, here are two young sun-flower plants, which I brought in from the garden. I placed one in water. The other I left lying on the table. The one on the table is dead. What does this show us?”
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.[1] Where do they get this water from?”
“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 water. And in this water there is but little plant-food. We saw this when we boiled away the clear water which covered the soil in the glass.
“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!