152 THE SCIENCE OF LIFE. 



The PORTULACACE^:, or Purslane family, are chiefly 

 herbaceous plants, found in dry, barren situations, or on 

 the sea-shore. Some of them have tuberous roots which 

 have been proposed as substitutes for the potato, as 

 Claytonia tuber osa, and Melloca tuber osa. The first is a 

 Siberian plant, the other a native of Peru. 



The Cactus family (CACTACE^E) contains many succu- 

 lent plants, destitute, for the most part, of leaves, the 

 place of which is supplied by fleshy stems of grotesque 

 figures. Some are angular, and grow to a height of 



FIG. 63. A Group of Cactacese. 



thirty feet; others are roundish, covered with stiff spines, 

 and not over a few inches high. Their flowers are often 

 large and beautiful, varying from pure white to rich 

 scarlet, or purple. Some are night-flowering, as the 

 Cereus grandiflorus. In Mexico and Southern Califor- 

 nia there are a large number of species, some of which 

 are of gigantic size. (Fig. 63.) 



