"And the flower makes three, doesn't it? But then there's the stalk, too. That makes four. There must be four parts." "There are a great many parts," nodded the Chief Gardener, "but there are only three principal parts--the root, the stem, and the leaf. To a botanist--one who studies plants and how they grow--the flower is only a branch of the stem, and its parts are leaves." "I suppose that is why rose-petals are called leaves," said little Prue. "I think it is." "But--but don't you think a flower _ought_ to be a principal part?" asked Davy. "Well, it is in a way. It is a particular kind of a principal part, made for a special purpose. But after all, it is really a branch, for it comes from a bud, just as other branches do, and it comes just where any branch would come. Many times you cannot tell whether a bud is going to make a flower or just leaves until it opens. And there are a few queer flowers in the world that can hardly be told from leaves even after they do open." II THERE ARE EXOGENS AND ENDOGENS "NOW let us tell the parts of a flower. That was what we were doing when you came up," said Davy. "And let me tell again," said little Prue. "I know I can get them right, this time." So little Prue told again, and got it almost right, though she did call anthers "panthers" again, just as the first time. "Now, Davy, it's your turn," said the Chief Gardener. Davy picked up a little pink flower which he had found in the grass. It was oxalis, or sorrel, and sometimes the children nibbled the sour leaves, calling it sour-grass. Of course, you must not forget that Davy was older than Prue, and perhaps a little more thoughtful. "This," he began, picking off the little green flower-casing, "is the calyx, and each little piece is called a sepal. This flower has five sepals in its calyx, and five petals in its corolla. These are the petals," and he pulled out the little pink flower-leaves, and laid them by the green sepals. Then he held it up for the Chief Gardener and little Prue to see. "Look at the stamens," he said. "They all grow together at the bottom." "That's because your sorrel is a Monadelphian," said the Chief Gardener. Davy looked puzzled. [Illustration: THE PISTIL AND STAMENS OF THE LILY] "I know what a Philadelphian is," said Prue. Davy laughed. "The words are very much alike," smiled the Chief Gardener. "They both mean brotherhood, and come from some old Greek words. Philadelphia means brotherly love, and Monadelphia means brotherly union. You see those stamens are all brothers and are joined together as one. All plants with such stamens are called Monadelphians." "A stamen has three parts," Davy went on, "its filament, its anther, and its pollen. The filament is the stem, the anther is its cap, and the pollen is the dust which falls on the pistil and helps to make the seed." [Illustration: A PISTIL AND CALYX AND A COMPLETE FLOWER]