HISTORY OF BRITISH FERNS.
The proportion borne by the Eerns 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 borne between these
two great divisions of vegetation, is reckoned at one Eern
to thirty-five flowering plants. In Scotland they stand relatively
as one in thirty-one.
The forms which exist among the Eerns are very diversified,
and this, 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 their leading features are concerned, 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 themselves
the majestic growth of the Palms, with the delicacy of the
lower Eerns, 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 marks left on the
falling away of the fronds; they grow to a height of from
twenty to fifty feet or more, from their tops sending out the
feathery fronds, often many feet in length, and yet so
delicate as to be put in motion by the gentlest breeze. On
some of the East Indian Islands the tree Eerns occur as
numerously as the crowded Eirs in our plantations; but
wherever they are found—from the plains to an elevation of
3.000 to 4,000 feet—the soil and atmosphere are full of
moisture. Very noble arborescent Eerns are found in New
Zealand and Tasmania.
The shrubby Eerns, those with short stems, surmounted
by tufted fronds, prevail rather at the tropics than at the
equatorial zone, and are found less frequently at the foot of
tropical mountains, than at an elevation of from 2,000 to
3.000 feet. Eerns of this aspect abound in the South Sea
Islands. Mr. Colenso describes one of the New Zealand
species as producing, from a main trunk twelve feet high,
fronds which form a droop often of eighteen fe e t; such
plants, standing singly on the bank of a purling rill of
water, being objects of surpassing beauty.
The herbaceous species are rather characteristic of the
temperate and colder zon es: not that their number in