Figure 24.14 Cactus flowers.

Chapter 24

the fleshy, flattened or cylindrical, often fluted stems carrying on the photosynthesis of the plants (Fig. 24.15). Many cacti can tolerate high temperatures, and some can withstand up to several years without moisture. They vary in size from pinheadlike forms to the giant saguaro (see Fig. 26.7) that can attain heights of 15 meters (50 feet) and weigh more than 4.5 metric tons (5 tons). Cacti are generally exceptionally slow-growing and, because they need so little care, make good house plants for sunny windows.

In 1944, a marine pilot was forced to bail out of his aircraft over the desert near Yuma, Arizona. Until he was rescued 5 days later, he survived the intense heat and low humidity of the area by chewing the juicy pulp of barrel cacti in the vicinity. Since then, the use of cacti for emergency fluids and food has been recommended in most survival manuals.

Most cacti have edible fruits, and only three cacti (peyote, living rock, and hedgehog cactus) are known to be poisonous. Prickly pear fruits are occasionally sold in American

Flowering Trees And Shrubs SouthwestPipe Desert Cactus PlantsFlowering Trees And Shrubs Southwest
Figure 24.15 Cacti. A. Prickly pear cacti. B. Peyote. C. A barrel cactus. D. An organ-pipe cactus.

Flowering Plants and Civilization 475

supermarkets and taste a little like pears. Prickly pear fruits also have seeds that Native Americans of the Southwest dried and ground for flour they mixed with water and used as an atole (thickened souplike) staple food. A good syrup is obtained from boiling the fruits of prickly pears and also those of the giant saguaros. In the past, cactus candy was made by partly drying strips of barrel cactus and boiling them in saguaro fruit syrup, but the cactus is now usually boiled in cane sugar syrup.

Native Americans of the Southwest used to scoop out barrel cacti, dry them, and use them for pots. They also mixed the sticky juice of prickly pear cacti in the mortar used in constructing their adobe huts. In Texas, a poultice of prickly pear stem was applied to spider bites. Hopi Indians chewed raw cholla cactus as a treatment for diarrhea, and the skeletons of these cacti were used for flower arrangements.

In the middle of the 19 th century, Australians planted a few imported prickly pear cacti in the dry interior. These cacti found no natural enemies in their new environment and multiplied rapidly, infesting more than 24 million hectares (60 million acres) within 75 years. In 1925, in an effort to control them, Australia introduced an Argentine moth among the cacti. The moth's caterpillars feed on prickly pear cacti and gradually brought the plants under control, making the land usable again.

Another cactus parasite, the cochineal insect (related to the mealybug, a common house plant pest), feeds on prickly pear cacti in Mexico. At one time, the insects were collected for a crimson dye they produce; the dye was used in lipstick and rouge before aniline dyes derived from coal tar were introduced in the 1930s.

Peyote cacti are small button-like plants that have no spines, with roots resembling those of carrots. They contain several drugs, the best known of which is mescaline, a powerful hallucinogen. Dried slices of peyote have been used in native religious ceremonies in Mexico for centuries and more recently by at least 30 tribes of Native Americans.

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