Michael Byrd, age 13, of Ypsilanti, Mich,,‑
How many different cactus plants are there?
The vast army of prickly cacti are natives of the New World, though some have been taken to Australia and other likely places where they thrive under conditions similar to those at home, In the New World they thrive in the southwestern states and the dry desert regions of Central and South America, On almost any day of the year, they add their drab greens to the dusty landscape. But after a rare desert rain, they burst into waxy blossoms and the desert becomes a garden of rainbow colors as far as the eye can see,
The cactus plants have the dry, warm deserts to themselves, for no other plants can survive there. They are large and small plants that developed special methods for hoarding the rare desert rains to keep themselves alive during the long droughts, Originally, perhaps, their ancestors were normal plants ‑ which waste a great deal of water by evaporation through the leaves. We do not know these original cactus ancestors and they may have developed from a wide assortment of plant families.
The botanist, then, could not count and classify the cacti on the basis of their origins, which he does not know. Instead, science groups them on the basis of the one feature they have in common ‑. their amazing success in coping with desert climate. They are classed in the plant family Cactusaceae and so far we have counted and named over a thousand of them. The Cactusaceae class is subdivided into orders, families and genera ‑ and each variety has a species name all its own.
Each cactus made sacrifices in order to enjoy the roomy desert, It gave up the papery leaves through which the water, taken up from the soil, tends to evaporate into the air, Leaves among cacti are very rare. The plant body is a swollen stem and the leaf‑like lobes are swollen twigs or branches.
The sturdy pioneer developed a thick, leathery coat to prevent the dry desert air from stealing the water stored in special cells inside its stems.
Most cacti can live on their stored water for years, But when the short, sharp showers drench the desert, they are all set to grab the water before it runs away or seeps into the sandy ground. The long roots spread out far and wide, just below the surface.
The store of water is a temptation to thirsty desert animals ‑ but the cactus plant has solved this problem also. Its leathery coat is studded with an army of prickles, just waiting to give, say, a thieving desert rat a sharp jab in the nose.
In the long desert drought, the cactus uses and loses some of its water. The fleshy stems, drab with desert dust, tend to wilt. Washed clean and green by a swift shower, their fleshy stems are soon fat with new water supplies and some of this wealth is used in a sudden burst of gaudy flowers. Several gallons of precious water, however, will sensibly be stored and the giant saguara cactus, tall as a silver birch tree, will store about 30 tons of water to support its wide trunk and branches until the next desert shower.