an inch after the tree had been blown over. The roots, which may often
be observed extending along the surface of the ground forty or fifty
yards from the trunk, also retain their vitality after the tree is laid
low; and the Portuguese now know that the best way to treat them is to
let them alone, for they occupy much more room when cut down than when
growing.

The wood is so spongy and soft that an axe can be struck in so far with
a good blow that there is great difficulty in pulling it out again.
In the dead mowana mentioned the concentric rings were well seen. The
average for a foot at three different places was eighty-one and a half
of these rings. Each of the laminae can be seen to be composed of two,
three, or four layers of ligneous tubes; but supposing each ring the
growth of one year, and the semidiameter of a mowana of one hundred feet
in circumference about seventeen feet, if the central point were in the
centre of the tree, then its age would lack some centuries of being as
old as the Christian era (1400). Though it possesses amazing vitality,
it is difficult to believe that this great baby-looking bulb or tree is
as old as the Pyramids.

The mopane-tree ('bauhinia') is remarkable for the little shade its
leaves afford. They fold together and stand nearly perpendicular during
the heat of the day, so that only the shadow of their edges comes to
the ground. On these leaves the small larvae of a winged insect appear
covered over with a sweet, gummy substance. The people collect this
in great quantities, and use it as food;* and the lopane--large
caterpillars three inches long, which feed on the leaves, and are seen
strung together--share the same fate.

* I am favored with Mr. Westwood's remarks on this insect as
follows:

"Taylor Institution, Oxford, July 9, 1857.

"The insect (and its secretion) on the leaves of the bauhinia,
and which is eaten by the Africans, proves to be a species of
Psylla, a genus of small, very active Homoptera, of which we
have one very common species in the box; but our species,
Psylla buxi, emits its secretion in the shape of very long,
white, cotton-like filaments. But there is a species in New
Holland, found on the leaves of the Eucalyptus, which emits a
secretion very similar to that of Dr. Livingstone's species.
This Australian secretion (and its insect originator) is known
by the name of wo-me-la, and, like Dr. Livingstone's, it is