Part 7

“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?

“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.

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.”

“Can you see any reason for this coiling before it reaches the twig?” As he spoke, Uncle George pulled a sweet-pea plant out from its supports, and the boys saw that the tendril was really a spiral spring. The plant could be pulled out a considerable length without breaking the tendril.

“You see,” Uncle George continued, “if it were not for that first coiling of the tendril—that is to say, if the tendril grew out straight and only began to twist when it reached the twig—the first breeze of wind would snap the plant from its supports and it would fall to the ground.

“Look now, at the young sweet-peas which we grew in the pot. They are without tendrils of any kind. This shows us, I think, that the sweet-pea was at one time a small plant, like its relative the clover. It grew in open places and did not have to struggle for light and air. But, by and by, when strong growing plants took up the soil, it became forced to produce climbing organs or become choked out. And, having turned its leaves into climbing or gripping organs, it made up for the loss of leaves by producing large stipules and green out-growths to stem and leaf.”

Exercises on Lesson V.

1. Draw a leaf of the wild rose and one of the sweet-pea side by side. 2. Make a list of all the climbing plants you know, and state how each climbs. 3. Look for stipules on the apple, pansy, and bean leaves—make sketches. 4. Those plants of the pea family which have many leaflets have smooth round stems. Those which have few leaflets have “winged” stems. Can you explain this?

VI.—THE GREAT WATER BEETLE.

During summer the boys paid many visits to the horse pond. Each time they went there they saw something to interest them.

Their uncle taught them to keep perfectly still while looking into the water. They soon came to know that this was the best way to study pond-life, for, whenever they moved, the creatures they were watching would dart out of sight.

One day, while they were both lying on the bank gazing into the pond, a huge black beetle came up to the surface of the water. It remained there for a few moments, with its head hanging downwards and its tail sticking right out of the water. Then it dived down out of sight. In a few minutes it came up again, and this time Frank’s net was under it before it could escape.

Just as Frank was putting it into the glass jar, Tom whispered, “Here is another one—quick, Frank!”

But Frank was too late; for before he could get the first beetle into the jar, the second one had dived to the bottom of the pond. The boys waited for a long time, hoping to see the other beetle again. At last their patience was rewarded. The beetle came up again to the surface. As soon as it did so, in went the net, and out came beetle number two.

“What big beauties,” said Frank. “I wonder what they are. Let us hurry home and show them to Uncle George.”

When they got home, their uncle placed the two beetles in a glass tank by themselves, so that they could be more easily observed.

“What do you call them, uncle?” asked Frank. “We have never seen such large, handsome beetles before.”

“Have you not?” his uncle replied. “I am surprised at that, for this beetle is found in nearly all our ponds and ditches. It has a long Latin name, which means Bordered Diver, but it is commonly known as the ‘great water beetle.’ There are several kinds of these diving beetles. This is the largest. Can you give me an idea of their size?”

And Uncle George handed Frank a small measuring rule which he carried in his pocket.

Frank looked at the beetles, and then moved his thumb nail along the rule.

“About an inch and a half in length,” he said.

“That is about right,” said his uncle. “Are these two beetles exactly alike?”

“They are both about the same shape and colour. One is slightly bigger than the other. They are both greenish-black above and brown below. There is a curious broad border of yellow all round the edge of their bodies,” said Tom.