41 strange forest 



to the giant saguaro which towers sometimes seventy-five 

 feet, weighs six or seven tons, and hves for as much as 

 two hundred years. Some eleven sorts of cactus have been 

 found only in Arizona, other kinds are more widespread. 

 But they all have the same general characteristics and em- 

 ploy very similar devices in their determination to make 

 a good best of desert living. 



Most have the succulent stems which store water, when 

 they can get it, to be saved for a non-rainy day — or month, 

 or even year. Leaves are vestigial or completely absent 

 because too much moisture would evaporate from them, 

 and the stems are green with chlorophyll so that they can 

 perform the functions of leaves. These stems are also often 

 coated with wax to economize water still further and 

 usually they are provided with formidable spines — partly 

 to discourage animals which would be only too glad to 

 use the succulence for their own purposes, partly because 

 spines limit the free circulation of the hot, desiccating 

 atmosphere, perhaps also because they provide broken 

 shade to the surface of the plant. 



All these devices have been independently invented by 

 other plant families which also moved into the desert. 

 Succulence, waxy coatings, and reduced or absent leaves 

 are common. To the layman, indeed, any plant which 

 exhibits all these characteristics is commonly called 

 ''a cactus," though he is often wrong because the true 

 cactus is a member of a family strongly marked in other 

 ways. That graceful spray of ten-foot wands tipped with 

 flame-colored flowers and called ocotillo is no more a 

 cactus because it has spines and bears no leaves except 

 during wet weather than a butterfly is a bird because it 

 has wings. 



