Rollo found his wheelbarrow in its proper place, and trundled it along into the garden. "Father," said he, "what trees are you going to prune first?" "O, I am going to begin at the back side of the garden, and prune them all, advancing regularly to the front." "What is the saw for?" said Rollo. "To saw off the large branches, that I can't cut off easily with a knife." "But I should not think you would want to saw off any large branches, for so you will lose all the apples that would grow on them next year." "Why, sometimes, the branches are dead, and then they would do no good, but only be in the way." "But do they do any hurt?" said Rollo. "Why, they look badly." "But, I mean, would they do any actual hurt to the tree?" "Why, I don't know," said his father; "perhaps they would not. At any rate, if I cut them off pretty close to the living part of the tree, the bark will then gradually extend out over the little stump that I leave, and finally cover it over, and take it all in, as it were." By this time, Rollo and his father had reached the back side of the garden, and his father showed him the place where he had cut off a limb the year before, and he saw how the fresh young bark had protruded itself all around it, and was spreading in towards the centre so as to cover it over. Rollo then saw that it was better that all old dead limbs should be cut off. "That's curious," said Rollo. "Yes, very curious," said his father. "A tree will take in, and cover up, almost any thing that is fastened to the wood, in the same manner." "Will it?" said Rollo. "Yes," said his father. "If you drive a nail into a tree, the bark will, after a time, cover it over entirely. Sometimes people find things in old trees, which were put upon them when they were young." "How big things?" said Rollo. "O, I don't know exactly how big. The tree will make an effort to enclose any thing small or large. Only, if it is very large, it will take a great while to enclose it, and it might be so large that it never could enclose it." "Well, father, how large must it be so that the tree never could enclose it?" "O, I don't know, exactly. Once I saw a tree that was growing very near a rock. After a time it came in contact with it, and it grew and pressed against it, until the rock crowded into the wood. Then the bark began to protrude in every direction along the rock, as if it was making an effort to spread out and take the rock all in. But I don't think it will ever succeed; for the rock was part of a ledge in a pretty large hill." "What a silly tree!" said Rollo. "Father, I believe I will try the experiment some time," continued Rollo, after a pause. "Very well," said his father. "What shall I put into the tree?" asked Rollo. "You might put in a cent," said his father, "and then, if it should get fairly enclosed, I presume the tree will keep it safe for you a good many years."