126 TROPICAL PLANTS 



three, or even four, feet high near its base. These crests, which 

 are very thin but perfectly smooth, regularly follow all the 

 sinuosities of the root, and thus form, to a considerable dis- 

 tance round the tree, a labyrinth of the strangest appearance. 

 Large spaces of swampy ground are often covered with their 

 windings, and it is no easy matter to walk on the sharp 

 edges of these vertical bands, whose interstices are generally 

 filled with deep mud. On being struck, the larger crests emit 

 a deep sonorous sound, like that of a kettledrum. 



The thorns and spines with which many European plants 

 are armed, give but a faint idea of the size which these de- 

 fensive weapons attain in the tropical zone. The cactuses, the 

 acacias, and many of the palm trees, bristle with sharp-pointed 

 shafts, affording ample protection against the attacks of 

 hungry animals, and might appropriately be called vegetable 

 hedge-hogs, or porcupines. The Toddalia aculeata, a climbing 

 plant, very common in the hill-jungles of Ceylon, is thickly 

 studded with knobs, about half an inch high, and from the 

 extremity of each a thorn protrudes, as large and sharp as the 

 bill of a sparrow-hawk. 



The black twigs of the buffalo-thorn {Acacia latronum) 

 a low shrub, abounding in northern Ceylon, are beset at 

 every joint by a pair of thorns set opposite each other, like 

 the horns of an ox, as sharp as a needle, from two to three 

 inches in length, and thicker at the base than the stem they 

 grow on; and the Acacia tomentosa, another member of the 

 same numerous genus, has thorns so large as to be called 

 the jungle-nail by Europeans, and the elephant-thorn by the 

 natives. In some of these thorny plants, the spines grow, not 

 singly, but in branching clusters, each point presenting a spike 

 as sharp as a lancet; and where these shrubs abound, they 

 render the forest absolutely impassable, even to animals of the 

 greatest size and strength. 



The formidable thorny plants of the torrid zone, which are 

 often made use of by man to protect his fields and plantations 

 against wild beasts and robbers, have sometimes . even been 

 made to serve as a bulwark against hostile invasions. Thus 

 Sir Emerson Tennent informs us, that during the existence 

 of the Kandyan kingdom, before its conquest by the British^ 

 the frontier' forests were so thickened and defended by dense 



