220 VIEWS OF NATURE. 



The Cactus form (20), on the other hand, is almost peculiar 

 to the new continent; it is sometimes globular, sometimes 

 articulated, sometimes rising in tall polygonal columns 

 not unlike organ-pipes. This group forms the most 

 striking contrast with the Lily and Banana families, and be- 

 longs to that class of plants which Bernardin de St. Pierre 

 felicitously terms vegetable fountains of the Desert. In the 

 parched arid plains of South America, the thirsting animals 

 eagerly seek the Melon-cactus, a globular plant half-buried in 

 the dry sand, whose succulent interior is concealed by 

 formidable prickles. The stems of the columnar cactus attain 

 a height of more than 30 feet; their candelabra-like rami- 

 fications, frequently covered with lichens, reminding the tra- 

 veller, by some analogy in their physiognomy, of certain of 

 the African Euphorbias. 



While these plants form green Oases in the barren desert, 

 the Orchideae (21) shed beauty over the most desolate rocky 

 clefts, and the seared and blackened stems of those tropical 

 trees which have been discoloured by the action of light. 

 The Vanilla form is distinguished by its light green succulent 

 leaves, and by its variegated and singularly shaped blossoms. 

 Some of the orchideous flowers resemble in shape winged 

 insects, while others look like birds, attracted by the fragrance 

 of the honey vessels. An entire life would not suffice to enable 

 an artist, although limiting himself to the specimens afforded 

 by one circumscribed region, to depict the splendid Orchideae 

 which embellish the deep alpine valleys of the Peruvian 

 Andes. 



The form of the Casuarineae (22), leafless, like almost all 

 the species of Cactus, comprises a group of trees having 

 branches resembling the Equisetum, and is peculiar to the 

 islands of the Pacific and to the East Indies. Traces of this 

 type, which is certainly more singular than beautiful, may 

 however be found in other regions of the earth. Plumier'e 

 Equisetum altissimum, Forskal's Ephedra aphylla of North 



