quaint and uncanny-looking cactus, with its yellow blossoms and
bristling fruits that seem to grow paradoxically out of the edge of
thick fleshy leaves, is really a native of Italy, Spain, and North
Africa, where it now abounds on every sun-smitten hillside. Like Mr.
Henry James and Mr. Marion Crawford, the Barbary fig, as the French
call it, is, in point of fact, an American citizen, domiciled and half
naturalised on this side of the Atlantic, but redolent still at heart
of its Columbian origin. Nothing is more common, indeed, than to see
classical pictures of the Alma-Tadema school--not, of course, from the
brush of the master himself, who is impeccable in such details, but
fair works of decent imitators--in which Caia or Marcia leans
gracefully in her white stole on one pensive elbow against a marble
lintel, beside a courtyard decorated with a Pompeian basin, and
overgrown with prickly pear or "American aloes." I need hardly say
that, as a matter of plain historical fact, neither cactuses nor agaves
were known in Europe till long after Christopher Columbus had steered
his wandering bark to the sandy shores of Cat's Island in the Bahamas.
(I have seen Cat's Island with these very eyes, and can honestly assure
you that its shores _are_ sandy.) But this is only one among the many
pardonable little inaccuracies of painters, who thrust scarlet
geraniums from the Cape of Good Hope into the fingers of Aspasia, or
supply King Solomon in all his glory with Japanese lilies of the most
recent introduction.

At the present day, it is true, both the prickly-pear cactus and the
American agave (which the world at large insists upon confounding with
the aloe, a member of a totally distinct family) have spread themselves
in an apparently wild condition over all the rocky coasts both of
Southern Europe and of Northern Africa. The alien desert weeds have
fixed their roots firmly in the sunbaked clefts of Ligurian Apennines;
the tall candelabrum of the western agave has reared its great spike of
branching blossoms (which flower, not once in a century, as legend
avers, but once in some fifteen years or so) on all the basking
hillsides of the Mauritanian Atlas. But for the origin, and therefore
for the evolutionary history, of either plant, we must look away from
the shore of the inland sea to the arid expanse of the Mexican desert.
It was there, among the sweltering rocks of the Tierras Calientes, that
these ungainly cactuses first lear