TEOPICAL FOEEST. 275 



palms lifted their heavy crowns throughout the struggling 

 mass ; arborescent ferns,* which spring, with a palm-like 

 growth, to a height of forty feet, although native to the 

 temperate heights of the Cordilleras, were still occasionally 

 seen ; the equisetum, a cryptogamous plant, congener of 

 our northern scouring rush, attained a height of twenty 

 feet ; while arborescent grasses, shooting up forty feet 

 above us, impressed us with the capabilities of a tropical 

 nature. These familiar illustrations will enable one to 

 form some conception of the luxuriance of the vegetation 

 here, and the gigantic size attained by specific forms. 

 But these do not constitute the frame-work of the forest. 

 This is formed by the trunks of exogenous trees similar in 

 appearance to northern arboreal forms. The diameter of 

 these is not so striking as their great height. This fram- 

 ing is filled in with every form of vegetation ; parasites 

 and epiphytes, the aerial roots of the latter often reaching 

 down from the highest trees to the ground, load the 

 branches ; while gray, sombre, arboreous mosses lend a 

 peculiarly melancholy aspect to the old forest-monarchs ; 

 vines encircle the trunks, and, looping, twisting, and inter- 

 twining, form a perfect maze of cordage. Humble i)lants 

 of strange types form the lower stratum of the forest, 

 constituting an almost solid mass of vegetation, through 

 which it is often impossible to penetrate. As the sun 

 scarcely enters the depths of these primeval forests, every 

 thing is saturated with moisture, which humidity afibrds 

 one of the chief requisites for that giant vegetation which 

 we find upon the flanks of the Andes and throughout the 

 valley of the Amazons. We found the forest at least 



* We obtained sections of this gigantic plant eight inches in diam- 

 eter. Darwin measured some in Van Diemen's Land six feet in circum- 

 ference. The species are numerous, and, as Kumboldt observes, are 

 confined almost exclusively to the tropics, but there preferring temperate 

 altitudes. 



