DISTRIBUTION AND TOPOGRAPHICAL ASPECT. S3 
The proportion borne by the Ferns to the whole mass of 
flowering plants in the torrid zone, is stated at erne 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 great divisions of vegetation 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 are principally confined to the torrid zone, their 
slender waving trunks often beautifully pitted by the 
D 
