1. Caterpillar, Pupa, and perfect Insect of Tiger Moth 2. Caterpillar, Pupa, and perfect Insect of Magpie Moth 3. White (Cabbage) Butterfly, Male and Female, with Caterpillar and Pupa “These are marks where leaves once grew upon it,” his uncle remarked. “Notice that the primrose leaves form a rosette on the top of this underground stem.” “Is there any reason for these plants having their stems under ground?” Tom asked. “There is a reason for everything in nature, my boy. Can’t you see any reason for this yourself?” “I see one, I think,” said Frank; “it enables the plant to creep out to new soil.” “That is one very good reason, Frank. Now, why should it seek other soil?” “For food!” “That is right, Frank. Those plants which have underground stems seem to die down every autumn; but they are alive all the time under ground, safe from the frosts and bitter winds which kill tender plants. And they peep up in a new place in spring. [Illustration: Anemone.] “Now I want you to tell me why these underground stems are swollen out so. It cannot be for strength, for creeping stems don’t require to be strong. “Fetch me a raw potato, Tom, please! “Now,” Uncle George continued, “tell me what this potato is.” “It is an underground stem,” said Frank. “Yes! Why is it swollen? What do we use the potato for?” “For food. Oh, I know,” said Frank, “it is a food store.” [Illustration: Primrose.] [Illustration: Pilewort, showing Roots.] “Of course,” said his uncle. “It is a supply of food gathered up this year for next year’s plant. Look at the roots of the lesser celandine. I see Tom has drawn them. They are swollen. Are they roots, or underground stems?” “They have neither leaf marks on them, nor buds,” said Frank, “I think they must be roots.” “They _are_ roots,” said Uncle George, “but they are food supplies all the same. “There are other underground stems that grow quickly. Good examples of these are mint, couch grass, and sand sedge. The underground stems of these plants grow so fast that they are always occupying new ground. They have therefore no need to store up a food supply like their slower growing neighbours the primrose, potato, anemone, iris, and many others.” Exercises on Lesson XI. 1. Dig up a primrose plant, and make a rough sketch showing underground stem, roots, and leaves. 2. An underground stem may be of use to a plant in three different ways. Can you name them? 3. There are two distinct kinds of underground stems—those that grow quickly and those that grow slowly. Name three of each kind, and tell how they differ in shape. 4. Compare a potato with a horse-chestnut twig. Supposing your twig to be swollen out with plant-food, what parts of it do the “eyes” of the potato represent? What do the {scars/marks} near the “eyes” represent?