Tree-ferns thrive luxuriantly in Van
Diemen's Land (latitude 45 degrees), and I measured one trunk no
less than six feet in circumference. An arborescent fern was found
by Forster in New Zealand in 46 degrees, where orchideous plants
are parasitical on the trees. In the Auckland Islands, ferns,
according to Dr. Dieffenbach have trunks so thick and high that
they may be almost called tree-ferns; and in these islands, and
even as far south as latitude 55 degrees in the Macquarie Islands,
parrots abound. (11/10. See the German Translation of this Journal;
and for the other facts Mr. Brown's Appendix to Flinders's
"Voyage.")
As the height of the plane of perpetual snow seems chiefly to be
determined by the extreme heat of the summer, rather than by the
mean temperature of the year, we ought not to be surprised at its
descent in the Strait of Magellan, where the summer is so cool, to
only 3500 or 4000 feet above the level of the sea; although in
Norway, we must travel to between latitude 67 and 70 degrees north,
that is, about 14 degrees nearer the pole, to meet with perpetual
snow at this low level. The difference in height, namely, about
9000 feet, between the snow-line on the Cordillera behind Chiloe
(with its highest points ranging from only 5600 to 7500 feet) and
in central Chile (a distance of only 9 degrees of latitude), is
truly wonderful.
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