On the north coast of Africa the camels delight in crunching the juicy leaves of the same plant.

I have often been amused in watching the camel-drivers' efforts to get their trains of laden beasts along the narrow sandy lanes of Tangier, between hedges of prickly pears, where the camels with their long necks could reach the tempting lobes on both sides of the way.
In this thirsty season, while the cattle in the Mexican plains derive moisture from the cactus, the aloe provides for man a substitute for water.

It frequently happened to us to go from rancho to rancho asking for water in vain, though pulque was to be had in abundance.
To attempt any description of the varied forms of cactus in Mexico would be out of the question.

In the northern provinces alone, botanists have described above eight hundred species.

The most striking we met with were the prickly pear (cactus opuntia), the organo, the night-blowing cereus, the various mamillarias--dome-shaped mounds covered with thorns, varying in diameter from an inch to six or eight feet--and the greybeard, _el viejo,_ "the old man," as our guide called them, upright pillars like street-posts, and covered with grey wool-like filaments.
Getting to the top of the ravine again, we found an old Indian milking an aloe, which flourishes here, though a little further down the climate is too hot for it to produce pulque.