THE TROPICAL ZONE. 83 



in spiral lines round the tall stems, and cover 

 them to the top. Some of these are upright, 

 others climbing plants, and are never branched 

 except when very old. Some very singular 

 species of pandanus have their trunks covered 

 with roots, which descend to the ground like 

 tightly -drawn cords, and support the main 

 trunk. One species (Pandanus odoratissimus) 

 is very common in the South Sea Islands ; its 

 flowers are of such delightful fragrance, that it 

 is often cultivated in Egypt and Arabia for 

 their sake. Its fruit reaches the size of a 

 child's head, and much resembles the pine 

 apple. The pine apple tribe are especially 

 luxuriant in this, as well as in the equatorial 

 zone. The pine apple, which is cultivated in 

 our hot-houses, is found wild in abundance in 

 the Molucca Islands, and in many parts both 

 of Asia and America. In Surinam, Brazil, and 

 the Indies, it is used for inclosing the fields, 

 and forms thick hedges, while its sharp-edged 

 and toothed leaves effectually keep out all ani- 

 mals. It was first cultivated in England at the 

 end of the seventeenth century, but so successful 

 have been the efforts to improve its cultivation, 

 that the fruit grown in England is more prized 

 than that cultivated abroad. 



The multitude of islands, termed Polynesia, 

 form a botanical district by themselves. Com- 

 posite, or syngenesious plants, with tree ferns, 

 constitute the principal portion of the vegeta- 

 tion. Ferns are so numerous that there is one 

 species of them for every three or four flower- 



