experiments made with this extraordinary exotic, the inhabitant of an
arid sandy soil, to the Horticultural Society of London. That succulents
should be found clothing in patches the surface of the burning desert is
a phenomenon not the least wonderful in the geographical history of
vegetation.

In Cockburn's _Voyages_ we find an interesting account of a tree in
South America, which yielded a plentiful supply of water by a kind of
distillatory process: this tree was met with near the mountainous
district of Vera Paz. The party were attracted to it from a distance,
the ground appearing wet around it; and the peculiarity was the more
striking, as no rain had fallen for six months previous. "At last," says
he, "to our great astonishment, as well as joy, we saw water dropping,
or, as it were, distilling fast from the end of every leaf of this
wonderful tree; at least it was so with us, who had been labouring four
days through extreme heat without receiving the least moisture, and
were now almost expiring for want of it." The testimony of travellers
is too often enshrined among the fabulous; and their credentials either
altogether rejected by some, or at least received "cum grano salis."
Bruce of Kinnaird forms the most remarkable example of this kind, and
the caricature of Baron Munchausen consigned the whole to sarcasm
and ridicule; and yet the time is come when the more remarkable
circumstances and phenomena mentioned by this traveller, verified by
Lord Valentia, Mr. Salt, &c. are received as well accredited facts.
The curious phenomenon mentioned by Cockburn finds an interesting and
beautiful counterpart in two plants--namely, the _C_alla Aethiopica
and Agapanthus umbellatus, in both of which, after a copious watering,
the water will be seen to drop from the tips of the leaves; a
phenomenon, as far as I know, not hitherto recorded.

The great rivers of the continent of Europe have their source of supply
in the glaciers; but many of the rivers in the New World owe their
origin to the extensive forests of America, and their destruction might
dry up many a rivulet, and thus again convert the luxuriant valley into
an arid and sterile waste; carried farther, the principle extends to the
great features of the globe. What the glaciers effect among the higher
regions of the Alps, the _P_inus _Cembra_. and _L_arix communis
accomplish at lower elevations; and many a mountain rivulet owes its
existence to their influence. It rains