find one that was not tenanted by ants. I
noticed three different species, all, as far as I know, confined to the
trumpet tree, and all farming scale insects. As in the bull's-horn
thorn, there is never more than one species of ant on the same tree.

In some species of evergreen shrub there is a direct provision of houses
for the ants. In each leaf, at the base of the laminae, the petiole, or
stalk, is furnished with a couple of pouches, divided from each other by
the midrib. Into each of these pouches there is an entrance from the
lower side of the leaf. I noticed them first in Northern Brazil, in the
province of Maranham; and afterwards at Para. Every pouch was occupied
by a nest of small black ants; and if the leaf was shaken ever so
little, they would rush out and scour all over it in search of the
aggressor. I must have tested some hundreds of leaves, and never shook
one without the ants coming out, excepting one sickly-looking plant at
Para. In many of the pouches I noticed the eggs and young ants, and in
some I saw a few dark-colored scale insects or plant lice; but my
attention had not been at that time directed to the latter as supplying
the ants with food, and I did not examine a sufficient number of pouches
to determine whether they were constant occupants of the nests or not;
but my experience since with the trumpet trees would lead me to expect
that they were. If so, we have an instance of two insects and a plant
living together, and all benefited by the companionship. The leaves of
the plant are guarded by the ants; the ants are provided with houses by
the plant, and food by the scale insects and plant lice; and the latter
are effectually protected by the ants in their common habitation.

Amongst the numerous plants that do not provide houses, but attract ants
to their leaves and flower buds by means of glands secreting a
honey-like liquid, are many orchids, and I think all the species of
passion flowers. I had the common red passion flower growing over the
front on my verandah, where it was continually under my notice. It had
honey-secreting glands on its young leaves and on the sepals of the
flower buds. For two years I noticed that the glands were constantly
attended by a small ant, and, night and day, every young leaf and every
flower bud had a few on them. They did not sting, but attacked and bit
my finger when I touched the plant. I have no doubt that the primary
object of these honey-glands was to a