ve several in the United States, but none which are as active. This is
called Venus' Fly Trap."

"That is curious," remarked Harry. "I wouldn't have paid any attention
to it but I saw a fly alight on it, and these little feelers seemed to
close around it, and hold it."

"It works on that plan exactly. It is in that way it gets its food."

"But why should the feelers be able to grasp the fly the moment it
touches the leaf?"

[Illustration: _Fig. 16. Venus' Fly-Trap._]

"Do you recall about what the Professor told you of the peculiar power
of plants to absorb food of particular kinds by a faculty called
_irritability_?"

"Yes; I remember."

"By means of that, plants are enabled to select just the kinds of
substances that they want, and can digest. If you will carefully notice
the leaf, after it has seized a fly it will be observed that the leaf
exudes a watery substance, and that has the property of digesting the
fly, or of converting the liquid part of the insect into a form of food
which is taken through the leaf, and from the leaf it goes into the
plant itself."

"I thought plants got their food from the roots only?"

"Leaves are just the same as roots. They are terminals, and moisture as
well as foods, such, for instance, as nitrogen, is absorbed and fed to
the plant through the leaves."

As they progressed they could see evidences of human occupation, and in
many places the remains of fire. It was while making a detour from the
regular route taken by John that they saw the first startling thing.

It was found at a place where a rude hut was discovered in a dilapidated
condition. Directly behind the hut was a raised sort of dais, supported
on two posts, and this was filled with human skulls, all in an advanced
stage of decay.

It was noticed only by accident, as the area around the hut was thickly
grown up by the vegetation. The boys were naturally startled at the
sight.

"What does that mean?" asked Harry.

John replied: "This is evidence that the people here are head hunters."

"What do you mean by _head hunters_?"

"Certain savages have the belief that their importance depends on the
number of heads they can capture."

"Where do they get them?"

"It is necessary for them to kill their enemies, and impale the heads,
or nail them up to their huts."

"Is it a religious ceremony?"

"In some cases that is so. In some tribes the object is merely to show
bravery and manliness. The more heads a m