49° 



POPULAR SCIENCE MONTHLY. 



The seeds of the cholla, like those of several allied species, rarely 

 if ever germinate on the open mesa. In eight years of observation 

 in its center of distribution I never found a seedling of this plant 

 growing wild. It spreads almost entirely by vegetal dissemination, 

 i. e., by the ends of the branches becoming detached and transported 

 often long distances from the mother plant. 



The cholla is perfectly adapted not only for the easy detachment of 

 the ends of the branches, but for their wide dissemination as well. The 

 fruit which hangs from the tree in long, pendulous clusters as illus- 

 trated in Fig. 6 is within easy reach of cattle and other large animals. 



Fig. 5. Were it not foe its Formidable Armor of Barbed Spines the Cholla 

 would soon be destroyed by animals. 



These clusters of succulent fruits are without spines and are for the 

 most part sterile. The fruit from the standpoint of seed production 

 is of very little service to the plant in aiding in its perpetuation and 

 dissemination. Its chief service appears to be to entice animals to the 

 plant that the fragile ends of the branches which become detached at 

 the slightest disturbance may adhere to them and become scattered far 

 and wide. 



In order that these fruits may best serve their purpose they are 

 succulent, unarmed and as eagerly eaten by animals when green as when 

 ripe. Moreover they often remain on the plant for two or more years 

 if undisturbed. During periods of scanty forage in the region where 

 the cholla grows it is not an uncommon sight to see the range cattle 

 with their heads literallv covered with these formidable cactus burs 



