AMERICAN WILD FLOWERS 



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eight feet and a diameter of one foot (fig. 271). Each plant is 

 marked with twenty or more longitudinal ribs, armed with stout 

 reddish or yellowish spines which completely protect the surface 

 of the plant; the flowers are usually yellow, with purplish sepals. 



Fig. 272. — The sahuaro cactus of southern Arizona, which grows to tree size, is 

 our most spectacular native plant. 



Most spectacular of our native cacti are the torch cacti or 

 Cereus cacti, columnar and fluted plants which grow to a height 

 of thirty or forty feet. The largest species is the giant Sahuaro 

 (fig. 272) whose massive succulent stem is divided into longi- 

 tudinal ridges separated by deep furrows. Waxy white flowers, 

 made up of numerous petals and thousands of stamens, are 

 produced at the tops of the trunks; each funnel-shaped flower 



