"Well, that's pretty good, Davy, and is true enough, but it isn't just the best way to reason. Now, Prue, why did you think it was an Exogen?" "Because the stem is hollow, and makes a ring when you cut off a little slice of it, and because the bloom part is in five pieces." "Sharp eyes," nodded the Chief Gardener, "but Davy is right. There is not always a pith in the endogens. Pipe-stems and fish-poles are hollow, but the cane we make them of is an Endogen, too. And as for the bloom part of this grass, it is a sort of a tassel, like that of the corn. The real blooms are very tiny--too small for us to examine. And then, perhaps, some insect or bird has nipped some of it away. I think I must tell you a little more about leaves, so Davy won't have to know that grass is an Endogen because corn is, and so you won't be mistaken. Suppose, Davy, you try to tell me how many kinds of leaves there are." Davy looked quite helpless. "It would take a hundred years," he said. "Why, no," said Prue. "There are just two kinds. Exogens and Endogens." Davy laughed, and the Chief Gardener laughed with him. "But you are right, Prue, in one way," he said. "There are just two kinds of leaves--simple and compound. A simple leaf is a leaf of just one blade, like a grass leaf, or the leaf of a morning-glory. A compound leaf is a leaf made up of several blades, like a bean leaf, which you know is divided into three parts. Of course, there are hundreds of shapes and thousands of species of leaves, but there are just two great kinds, simple and compound. Suppose, Davy, you look about and bring me three compound leaves, and you, Prue, try to find three simple leaves, and let's see what they are." The children jumped up quickly, and wandered out into the sunny garden, looking as they went. The Chief Gardener heard them chatting, as they looked this way and that. Presently they returned with what they had found. Little Prue climbed up in his lap. "Look at mine first!" she said, holding them out, and fanning herself with her little hat. Davy sat down by them, and looked his collection over to be sure they were right. "Well, Prue, let's see what you have," began the Chief Gardener. "One peach leaf--that's simple enough. Then here's a lily leaf--that's simple, too. But what's this? It looks as if it came from a Virginia creeper. But where's the rest of it? That's only part of a leaf." "I told Prue that," said Davy, "and I brought a whole one for one of my compound leaves." Davy held up what he had brought. The Chief Gardener took the stem of the Virginia creeper. Branching from it were five little stems with a small leaf on each. Prue had taken one of these to be a complete leaf, when it was really only a part of one compound leaf divided into five parts. "You see, Prue, there is only one stem that joins the main stalk," explained the Chief Gardener. "Whatever branches out from that stem is a part of that leaf. What else have you brought, Davy?"