DISTRIBUTION AND TOPOGIIAPHICAL ASPECT. S3 



The proportion borne by the Ferns to the whole mass of 

 flowering plants in the torrid zone, is stated at one in 

 twenty ; in the temperate zone at one in seventy ; and in 

 the frigid zone at an average of one in eight. In the most 

 northern parts of the Arctic zone, none have yet been 

 discovered. In our own country, the proportion existing 

 between these two aireat divisions of vco;etation is reckoned 

 at one Fern to thirty-five flowering plants. In Scotland 

 they stand relatively as one in thirty-one. 



The forms which exist among the Ferns are very diver- 

 sified, and this diversity, no less than their variations of size 

 and habit, renders them conspicuous objects in the scenery 

 where they abound. They may all be classed under three 

 divisions, so far as the leading feature of habit is con- 

 cerned, namely, arborescent, shrubby, and herbaceous. 



It is the former class — the arborescent species — chiefly, 

 which exert a marked influence on the physiognomy of 

 nature, for, as Meyen well remarks, they unite in them- 

 selves the majestic growth of the Palms with the delicacy 

 of the lower Ferns, and thus attain a beauty to which 

 nature shows nothing similar. These truly arborescent 

 species arc principally confined to the torrid zone, their 

 slender waving trunks often beautifully pitted by the 



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