^] how they got that way 



did not exist in a wild state anywhere outside the Western 

 Hemisphere, it was not because they did not hke it any- 

 where else. 



Neither can it be because only in America did climatic 

 conditions or changes capable of developing drought- 

 resisting plants occur. As a matter of fact, many difiFerent 

 plant families in many parts of the world did develop 

 the special features of desert dwelling plants so that the 

 casual layman would unhesitatingly call them cacti. There 

 are succulent mulberries in Australia and Africa, succulent 

 passion flowers in Africa and, on one of the islands of the 

 Indian Ocean, there is a succulent member of the gourd 

 family which develops a sixteen-foot trunk like an inverted 

 carrot. 



Or suppose we take the case of the milkweeds. Nearly 

 everybody who has paid any attention to our native plants 

 in either the wet or dry regions is familiar with one or 

 another member of this family. In our deserts there are 

 several species and some of them have the narrow, hard, 

 dry leaves characteristic of so many plants growing in dry 

 air. Visitors from elsewhere must often have been sm*- 

 prised to see a cluster of unmistakable milkweed flowers 

 topping a plant which looks, at first sight, as though it 

 were clothed in pine needles. Nevertheless, no Arizona 

 species has a succulent, water-storing stem or looks any- 

 thing like a cactus. Yet in Africa and also in Asia there 

 are related plants which, though not spiny, look a good 

 deal hke cacti. They are nearly leafless and they store 

 moisture in their stems. 



But perhaps the most interesting case of all is that 

 of the African members of the cosmopolitan Euphorbia 

 family, of which the Arizona limber bush is a character- 



