It takes some sense to give even one minute of honest thought to the thing you are looking at. You know some children who never seem to have all their thoughts in one place at a time, and who in consequence never see anything really well. It is better to stop doing a thing altogether than to do it in a foolish sort of way; and it is foolish to start to do even the smallest thing, and yet not do it. The child who looks at even a leaf in a way to make it possible for him to draw the outline of that leaf five minutes later, is likely to be the child who goes in for both work and play with all his heart, and who comes out as far ahead on the playground as he does in the schoolroom. Now, after that lecture, which some of you need badly enough (and which I will tell you, as a great secret, I need not a little myself), I want to point out a few more of the things that are worth noticing in a leaf. But perhaps it is better to save them for another chapter. HAIRY LEAVES Notice always whether a leaf is smooth or hairy. Do you remember the mullein that sends up its tall spires over the hill pasture? The grayish leaves of this mullein are so hairy that they feel almost like wool. What is the use of all this hair? It is not likely that a plant would wrap itself in this hairy coat except for some good reason. It is believed that this coating of the mullein prevents animals from eating the leaves, and so destroying the plant. In the mouth, these hairs slip from the leaf blade, and cause a most unpleasant sensation. But usually the hairs on a leaf are helpful because they prevent too much perspiration or giving-off of water. The more freely the hot sun beats upon a leaf, the more quickly the water is drawn away from it. You can see just how this is by hanging a wet towel in front of the fire. In a very short time the heat from the burning coals draws the water from the towel. But put a screen between the fire and the towel, and the water passes off more slowly. Now, the hairs on that side of the leaf which faces the sun act as a screen from its fierce heat. We have learned how important it is that the leaf should not part with its water more quickly than the roots can make up the loss. We know that when a leaf does this, it wilts just as a leaf wilts when it is picked and cut off from its water supply, on account of the collapse of the walls of the many little cells which are emptied of water. So you can understand that plants which grow in dry, sunny places, where there is little drinking water for the roots, and where the sun beats constantly on the leaves, must take every care that there is no waste of water. And if you keep your eyes open, you will discover that many of the plants which grow in such places screen themselves from the full heat of the sun by a coat of hairs.