is a variety of Chica," he answered.

"What is Chica, anyhow?"

"The seeds are good for making burning oil. The inner bark furnishes a
fiber which resists all moisture; and the nuts possess a substance
which is well known all over the world as mucilage. It is recognized in
commerce as gum tragacanth."

"I saw different kinds there. Are they all useful?"

"Some species contain nuts which are very fine, but are never eaten raw.
They must be roasted."

[Illustration: _Fig. 10. Chica The Gum Plant._]

"When Jim and I were down there this morning we saw at least a dozen
different kinds of plants growing together in a space not three feet
square. We both wondered why each kept on growing in its own way, from
the same kind of soil. Now, don't the plants get all they are made of
from the same soil? And if that is so, why don't they grow to be the
same things?"

"Of course, like the animal kingdom, the germ of each is different, but
each takes the identical substances from the same soil, and converts
them into entirely different products. One will make a gum; the other
produces a kind of milk; others will turn out a hard substance, like the
outer portion of the nut; some will make a vegetable good to eat; others
will yield a poison, and yet all are from the same soil."

"That is what I mean. Even though the plants are different, why is it
that one will extract one thing and another something else?"

"It is due to what is called irritability or sensitiveness in plants.
One plant is sensitive to the flow of certain juices, and is irritated,
so that it is set into activity when different kinds of substances are
carried along the pores or deposited in the cells. As a result, this
irritation causes the plant to take only certain ones and reject others,
and its tissues are thus built up only by such elements as its
sensitiveness selects."

The training of the warriors with the new guns was a stirring sight for
the boys, who could not help but be present during most of the time
during the two days preceding the departure for the country of the
Tuolos.

Ralph and Tom begged permission to accompany the party, and this was a
natural request, because they had been rescued from this tribe the year
before.

It thus happened that the party of warriors, equipped as they had never
been before, left the village, with one of the wagons, which was loaded
with provisions and ammunition, and the boys took charge of the team.