to
extract the soda. The glasswort has leaves, it is true, but they are
thick and fleshy, continuous with the stem, and each one terminating in
a sharp, needle-like spine, which effectually protects the weed against
all browsing aggressors.

Now, wherever you get very dry and sandy conditions of soil, you get
this same type of cactus-like vegetation--_plantes grasses_, as the
French well call them. The species which exhibit it are not necessary
related to one another in any way; often they belong to most widely
distinct families; it is an adaptive resemblance alone, due to
similarity of external circumstances only. The plants have to fight
against the same difficulties, and they adopt for the most part the
same tactics to fight them with. In other words, any plant of whatever
family, which wishes to thrive in desert conditions, must almost, as a
matter of course, become thick and succulent, so as to store up water,
and must be protected by a stout epidermis to prevent its evaporation
under the fierce heat of the sunlight. They do not necessarily lose
their leaves in the process; but the jointed stem usually answers the
purpose of leaves under such conditions far better than any thin and
exposed blade could do in the arid air of a baking desert. And
therefore, as a rule, desert plants are leafless.

In India, for example, there are no cactuses. But I wouldn't advise you
to dispute the point with a peppery, fire-eating Anglo-Indian colonel.
I did so once, myself, at the risk of my life, at a _table d'hote_ on
the Continent; and the wonder is that I'm still alive to tell the
story. I had nothing but facts on my side, while the colonel had fists,
and probably pistols. And when I say no cactuses, I mean, of course, no
indigenous species; for prickly pears and epiphyllums may naturally be
planted by the hand of man anywhere. But what people take for thickets
of cactus in the Indian jungle are really thickets of cactus-like
spurges. In the dry soil of India, many spurges grow thick and
succulent, learn to suppress their leaves, and assume the bizarre forms
and quaint jointed appearance of the true cactuses. In flower and
fruit, however, they are euphorbias to the end; it is only in the thick
and fleshy stem that they resemble their nobler and more beautiful
Western rivals. No true cactus grows truly wild anywhere on earth
except in America. The family was developed there, and, till man
transplanted it, never succeeded in ga