There is a way to take hold of a nettle so that it cannot sting. The little poison-filled hairs all point _up_, as you see in the picture. So if you stroke the nettle or draw your hand over it from root to tip, it cannot hurt you. Your hand presses the hairs flat against the stem and they cannot stick into you. [Illustration: [Hairs]] Sometimes hairs branch and make a thick network, like felt, over the leaf. They do this in the mullein, and here is a picture of mullein hairs very highly magnified. Prickles and scales are made of cells as hairs are. All parts of the plant above ground and sometimes the roots are covered with skin, but only the parts above ground are covered with hairs or prickles. Some plants are abundantly supplied with these protections; others manage to get along without them. Plants very often have glands in their skins. These glands are merely cells which take certain things from the sap and pour them out on the outside of the plant. Glands secrete their fluids inside the skin cells, and these fluids finally break through the outer wall of the skin cell and so get to the surface, or else they pass through stomata specially provided for them. They sometimes cover the surface of the plant with a sticky substance, as is the case with young birch twigs. Glands also secrete the gum or resin which covers up the winter buds and keeps out the rain, and which makes the young leaves of the cherry shine so. Some plants secrete wax which covers leaves or stems or fruits. Bayberry berries are covered with white wax, of which fragrant candles can be made. Bayberry grows abundantly all along the New England coast, and friends of Thoreau used to make these fragrant candles as Christmas presents. Whenever Thoreau went to visit them, he insisted upon having a bayberry candle to go to bed by. The _bloom_ on cabbage leaves and on plums and other fruits is made of tiny scales of wax. [Illustration: BAYBERRY.] Wax is a very good substance to keep the plant dry. You may be sure the plant knows this and often uses it about the stomata. You see, the object is to allow water to pass freely _out_ of the stomata by evaporation, but not, as a rule, to pass _into_ them. So the clever plants often have wax instead of hairs as a protection to the stomata. It would not do at all to let the stomata get closed up, so they are always protected in some way. Sometimes little projections grow out of the skin, close to the stomata. The raindrops fall upon these little knobs and stay there, instead of settling down into the stomata. You see, the pegs are _very_ small, and when the rain falls on them there is a layer of air below them which the water cannot displace, and which prevents it from going any farther.