"Because," replied Forester, "where trees grow close together, the light and the air is excluded from the lower parts of the stems, and so branches cannot grow there. Nothing can grow without light and air."
"I've seen monstrous long potato sprouts grow in a dark cellar," said Marco.
"Yes," said Forester; "so have I. I did not think of that. But they don't grow very well."
"They grow pretty long, sometimes," replied Marco.
"At any rate," said Forester, "the branches of trees will not grow from the stems of the trees near the ground, in the woods; and this is of great importance, for, whenever a branch grows out, it makes a knot, extending in to the very centre of the tree. This would injure a pine log very much, as the knot would show in all the boards, and a knot is a great injury to a pine board, though it is of great benefit to a mahogany one."
"Why?" asked Marco.
"Because it gives the wood a beautiful variegated appearance when they get it smoothed. So that the more knotted and gnarled a log of mahogany is, the better. It makes the more beautiful wood. But in pine, it is not beauty, but facility of working, which is the great object. So they always want to get pine as smooth and straight-grained as possible. So that one of these trees that grow detached, in the fields, would not be of much value for lumber. It has so many branches, that the boards made from it would be full of knots."
"That is the reason, I suppose," said Marco, "why they don't cut them down, and make them into boards."
"Perhaps it is," replied Forester.
"Has pine any other very good qualities?" asked Marco.