262 THE PLANT WORLD 



now having become thoroughly heated up and supplied with 

 water drawn in by the network of roots, which ramify in 

 all directions from the bases of their thick stems immediately 

 underneath the surface of the soil, begin to open a series of 

 reddish and lemon-yellow flowers, to be followed by the 

 formation of a crown of maturing fruits which stay in place 

 until the middle of the following summer. The thick fleshy 

 walls of these fruits have a pleasant acid flavor very re- 

 freshing to the wayfarer, while the huge bodies of the plants 

 contain a store of sap readily available for quenchino; thirst, 

 a discovery that appears to have been made by Indians, in 

 both North and South America. M amillaria grahami, also 

 a cylindrical fleshy cactus, not over a half foot in height, 

 opens its beautiful flowers among the rocks in the foothills 

 at this time and the roster of the bloom of the cacti is com- 

 pleted until the return of another year. 



The seeds of the sahuaro, which are produced in 

 enormous quantities, are devoured by the birds before being 

 freed from the fruits, but of the great number that reach the 

 ground and germinate, not more than one in a million survive 

 and make the curious globular, plantlet a few inches in 

 height eventually destined to become a great cactus. The 

 seedlings of all of the cacti form a favorite food of a large 

 number of small animals, being juicy reservoirs of water 

 and containing enough other material to lead to their 

 destruction before sufl'icient armament has been formed for 

 their protection. 



Some plants, in the lives of which the supply of moisture 

 Is the controlling factor, start up again with the summer 

 rains in a season much warmer than earlier in the year in 

 which they have previously been active. Cassia covesii must 

 be reckoned among these, and its brownish pods opening in 

 August make a second liberal sowing of its seeds. Verbena 

 cHiata and Sphaeralcea pedata likewise respond to the stimu- 

 lation of increased moisture consequent on the summer rains, 

 but much less profusely, only occasional clumps in bloom 



