“Here is a rose leaf. It is composed of several leaflets, and at its base there are two small, brownish-green things called _stipules_. If we compare this leaf with the leaf of the sweet-pea, we find that in some points they are similar, but in others very different. [Illustration] Sweet-Pea. Edible Pea. “The rose leaf is called a compound leaf, because it is made up of many small leaflets. The sweet-pea leaf is also a compound leaf, but it has only two leaflets, and these are of enormous size. The rose leaf has two small stipules. The stipules of the sweet-pea leaf are large and green. “If I place the rose leaf beside a sweet-pea leaf, you will notice that the latter has _no upper leaflets_.” “It has tendrils ‘instead,’” said Frank. “Exactly!” said Uncle George. “These tendrils correspond to leaflets. Now, if the plant has been forced to turn all its leaflets, except two, into gripping organs, how does it manage to make up for this loss of green leaves? [Illustration: Young Edible Pea.] “We have already learned that plants take in food from the air by means of the green substance in their leaves. The more of this green substance a plant possesses, the more food it can take in from the air. If it sacrifices leaves in order to climb up to the light and air, its amount of the green material must be lessened. But the sweet-pea makes up for this loss of leaves. Can you see how it does so?” “The stipules are very large,” said Frank. “And the lower part of the leaf-stalk is very flat, broad, and green,” added Tom. “Very good,” said Uncle George, “but look at the long, slender stem. It has flat, green, ribbon-like outgrowths on each side throughout its whole length. So, you see, what the plant loses in leaves, it makes up in another way. “Let us now look at the ordinary pea plant. Its leaf has four pairs of leaflets and three pairs of tendrils besides the terminal tendril—seven tendrils altogether. The stipules here are also very large—much larger than those of the sweet-pea. But the stem is round and smooth. There are no green outgrowths. Here is a wild pea, which I found to-day, which has no leaves at all. All its leaflets have been turned into tendrils or gripping organs. But look at the enormous stipules it has! They are much bigger than ordinary pea leaves. [Illustration] A Wild Pea with no Leaves. Young Sweet-Peas have no Tendrils. “Let us now look at the tendrils of the sweet-pea, and see how they grip their supports. Notice that they begin to twist long before they reach the supporting twig. Then, when they have reached it, they twist round it _in the opposite way_—just like a piece of string, if you twist it at one end, it untwists at the other.”