EXOGENS. 159 



they abound. The arborescent Heaths (Casuarina] form 

 many of the gloomy woods of Australia. Still more 

 striking are the forms of the thorny Cactuses, (Fig. 63,) 

 consisting merely of fleshy stems and branches of singu- 

 lar shapes. The Yuccas of Mexico, the great African 

 Aloes, and the Grass-trees of Australia, with their solid 

 liliaceous leaves, of a dull green, afford a picture of im- 

 movable repose. The stiff, shining leaves of Pandanus, 

 or Screw Pine, arranged in spiral lines, contrast greatly 

 in the Sandwich Islands with the finely divided leaves 

 of the Fern, spreading in graceful elegance, and trem- 

 bling in the breeze. Between these two extremes is the 

 Palm-form, which gives most characteristic beauty to the 

 tropical world. Some Palms have feathered leaves, 

 others have fan-leaves, and in some of the umbrella 

 Palms the crown consists of a few fans elevated on long, 

 slender stalks. In all the inflorescence breaks from the 

 stem below the origin of the leaves, and the sheath 

 hangs down, often several feet long. The shape and 

 color of the fruit varies from the large triangular Cocoa- 

 nut to the berry of the Date. The aerial summits of 

 the Palms, projecting like a colonnade above the thicket, 

 and crowned with leaves, give them an air of beautiful 

 majesty. (Fig. 51.) Deciduous, or Leafy woods, (Fig. 

 61,) with their branching stems and broad foliage, form 

 dense, compact, vegetable masses, characteristic of tem- 

 perate climes. Wand-like forms, with narrow, fluttering 

 leaves, often covered with silvery down on the under 

 side, are represented by the Willow and Poplar, and in 

 the south of Europe by the Olive. The Conifers, or 

 Needle-leaved woods, are distinguished by their narrow, 



