EXTENSION OF THE ACOTYLEDONES. 21 



8. The native country of the Ferns lies in the be- 

 ginning of the Torrid Zone. They are not however 

 so exclusively found in that part of the world as the 

 palms are, which, under the perpendicular rays of the 

 sun, at the level of the sea, acquire the utmost luxu- 

 riance. Their native country lies, according to Hum- 

 boldt and Bonpland, in a pendent line above that of 

 the palms; where they are arboreous, resembling the 

 palms in their exterior shape : whereas, in the Tem- 

 perate and Frigid Zones, they are herbaceous, vege- 

 tating only in summer. According to Crantz, only 

 four species of ferns are common to Greenland j and 

 some species of them (Pteris crispa and Pteris arch- 

 angelica) remain, according to Wahleriberg, 1400 ft. 

 below the snow-line. Accordingly, the extension of 

 these plants is so represented, that the Tropical 

 Regions appear as their native country. 



9. The order of Dutch Rushes (Equisetacece) is par. 

 ticular to the Frigid and Temperate Zones, although 

 their native country cannot be accurately ascertained. 

 In consequence of their being cryptogamic plants, 

 they obtain a very low degree of perfection : shewing 

 however, in their membraneous structure, and in the 

 spikes (wherein they bear the buds of fructification), 

 a degree of perfection that becomes real in the grasses. 

 According to these circumstances, the native country 



