76 THE AMERICAN BOTANIST 



from a prickly pear and throws it into a basket on his left 

 while the buyer takes the juicy fruit and wends his way home- 

 ward undisturbed by the fear of pricking his fingers on the 

 clusters of minute little thorns that stud its surface. The 

 prickly pear is not a native of the Mediterranean countries. 

 It was introduced into Spain from Mexico in the days of the 

 Spanish conquerors and has now spread for and wide. The 

 cactus represents almost the acme of Nature's clever method 

 of adapting living forms to different types of environment. 

 Beginning with species of plants which inhabited the water, 

 she made a tremendous step forward when a few plants 

 learned to live upon land. Since that day the progress of 

 evolution has enabled vegetation to become more and more in- 

 dependent of a permanent and easily accessible supply of water. 

 Our commonest plants take water from the soil even when 

 there is so little that the human hand cannot feel the moisture. 

 As the damper parts of the earth's surface became fully occu- 

 pied, vegetation spread out into drier regions. In the last 

 age of geological time. Nature has outdone herself. She has 

 produced a plant which can grow to the estate of a lordly 

 succulent tree on mountain slopes so hot and sunny that for 

 months it is painful at noon to touch the heated rocks which 

 project among the patches of the thinnest scantiest soil. The 

 cacti are far from archaic ; they are the youngest and most 

 highly developed among the families of plants — the most suc- 

 cessful of living forms in the struggle with ardity ; the master- 

 piece of Nature in the greenest of all earth's deserts. — From 

 "The Greenest of Deserts" by Ellsivorth Huntington in 

 Harper's Magazine. 



