“Some time ago,” said Uncle George, “I promised to tell you something
about how plants arm themselves. And here, in this hedgerow, we have
some good examples of armed plants.”
“There is the stinging nettle,” said Tom, pointing to a large patch at
the roadside.
“The stinging nettle is certainly well protected,” said his uncle. “You
have only to touch any part of it lightly with your hand to find that
out. Every part of the plant is covered with small needle-shaped hairs.
These hairs are hollow and contain a poisonous juice. At the base of
each hair there is a bag filled with this juice, while the tip of each
is sharp and very brittle.
“When your hand touches a nettle—unless you grasp it tightly—the sharp
hair pierces the skin. It’s brittle point breaks off and the poisonous
juice is poured out.”
“Why is the nettle covered with these horrid stings?” asked Frank.
“To save it from being eaten up, of course. The nettle is a tender and
juicy plant, and, if it were not for its stings it would soon disappear
altogether.
“Now, here is another armed plant, the blackberry or bramble. The stem
and also the backs of the leaves are covered with large curved prickles.
These prickles not only protect the plant from grazing animals, but they
help it to climb and scramble up walls and hedges.
“If you try to pull a bramble branch down out of the hawthorn hedge, you
will find it rather difficult, for its large prickles are all turned one
way. They are really sharp hooks.”
“Here is a wild rose bush. It is also covered with large hooked
prickles,” said Frank.
“Yes, Tom, and, like the bramble, it threads its way among stronger and
taller plants.
“The wild gooseberry growing close beside it is also armed with
prickles. But the prickles of the gooseberry are for protecting its
tender leaves. It is not a climbing plant like the rose and bramble. The
raspberry also is covered with many sharp little prickles. There is a
clump of these plants growing at the other side of the road. Let us cut
off a small branch of each of these plants and take them home.”
[Illustration: Armed Plants.]
1. Thistle.
2. Blackberry.
3. Whin.
4. Barberry.
5. Raspberry.
6. Sloe.
7. Buttercup.
“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.”
Exercises on Lesson IX.
1. Take in twigs of hawthorn, barberry, holly, bramble, and
gooseberry. Examine, and sketch them so as to show their
protective parts.
2. Grow a small whin bush in a pot and water it daily. Note that the
_new growth_ it makes is tender, and that _no spines_ are
produced.
3. Some plants are covered with dense woolly hairs. These are seldom
eaten by cattle. Can you explain why?
4. Make a list of all the armed plants you know, and tell how each is
protected.