boring beetle, and the way nature has of helping her children to
protect themselves.

The thistle of the meadow is as safe from hungry cattle as though
fenced in by barbed wire. A cow must be starving that would care
to flavor her luncheon with the needles that the thistle bears.
The common skunk cabbage would make a tempting meal for her after
a winter of dry feeding, had not Nature given it an odor that
disgusts even a spring-time appetite. The milkweed welcomes the
bees and flies that help to distribute her pollen where she wants
it spread, but she has her own way of punishing the useless
thieves that trespass up her stalk. Wherever the hooks of an
insect's feet pierce her tender skin, she pours out a milky juice
to entangle its feet and body, and it is a lucky bug that succeeds
in escaping before this juice hardens, and holds him a prisoner
condemned to die.

All over the world there are plants with the same ability that the
milkweed has, but it is especially true of certain trees and vines
of the tropics. As soon as the little beetle begins to bore into
the bark of one of these trees, there pours out a sticky, milky
fluid that kills the insect at once. If this were all, the wound
would remain open, ready for the next robber who came along. In
order that the break may be healed, a cement is necessary, but not
a hard, unyielding one, for that would crumble away with the
motion of the tree in the wind.

So with Mother Nature's perfection in doing things, the very plant
juice that has done duty as a poison is hardened into an elastic
stopper. with the result that, no matter how far the tree may sway