“This is the most prickly plant of all,” said Frank, as he halted before a huge thistle. “You can scarcely touch it without getting severely pricked.” “The thistle is well armed,” said Uncle George. “There are sharp prickles on its leaves, on its stem, and on its flowers.” As they walked down the road they came upon a mass of whin bushes. “Here,” said Uncle George, “we have a plant which has turned its leaves into sharp spines.” He bent down and pulled up a tiny plant which was growing under the larger gorse bushes. “Look at this little plant, boys. This is a young whin plant.” “But it is not a bit like the whin, Uncle George,” said Tom. “Its leaves are soft and flat. They are more like clover leaves. There are no spines or prickles on this little plant.” “That is so, Tom; but still it is a young whin plant. [Illustration: Young Whins.] “There are a great many of these young whins growing under the older bushes. Let us take a few of them home. If we grow one of them in a pot, and supply it with plenty of water, we will find that it will _never_ produce sharp prickles.” “That is very wonderful,” said Frank. “It is,” said Uncle George, “and it teaches us something of the whin’s history. Like the nettle, the whin is a juicy plant, and, if it were not for its prickles, would be eaten by cows, sheep, and horses. In fact, some farmers give whins to their horses. Of course the whins are passed through a mill first. The mill crushes the whins and destroys the prickles. “It shows us that many, many years ago the whin was a soft-leaved plant like the clover. It grew in moist soil. But by and by other plants invaded the land. These plants grew more quickly than the whin, and choked it out of the rich moist soil. Forced to grow upon bare hill-sides and commons, the soft-leaved juicy whin would be destroyed by grazing animals if it did not arm itself with sharp spines. “Here is the blackthorn or sloe. It bears many hard, sharp-pointed spines. Yet, if we grow a sloe plant in the garden, we find that its sharp spines gradually disappear. They become branches bearing leaves and flowers. “But plants have other ways of protecting themselves against animals. Look through the hedge into the meadow and you will notice that while the grass has been eaten bare, there are other plants which have been left to grow up untouched. Buttercups grow up all over the field, and tall ragwort plants. How is it that the cows do not eat these plants? They are not armed with spines or prickles. “They protect themselves in another way. They contain bitter or poisonous juices. No cow will eat a buttercup. If it did so it would be ill and uncomfortable for a time. “I want you to notice, boys, that—with the exception of those plants, like the bramble and wild rose, which use their prickles for climbing as well as for protection—all our armed plants grow in exposed places. The thistle and whin are good examples of this.”