Widely different are the ant-house plants, of which North Queensland has
two genera. One is purely an epiphyte, growing attached to a tree like
many of the orchids. In both genera the gouty stems are hollow, a feature
of which ants take advantage; they are merely occupiers, not the makers
of their homes. Few, if any, of the plants are uninhabited by a resentful
swarm, ready to attack whomsoever may presume to interfere with it. It is
discomposing to the uninitiated to find the curious "orchid," laboriously
wrenched from a tree, overflowing with stinging and pungent ants, nor is
he likely to reflect that the association between the plant and the
insect may be more than accidental.

Some of the commonest wattles exhibit singularity of foliage well worth
notice. Upon the germination of the seeds the primary leaves are pinnate.
After a brief period this pretty foliage is succeeded by a
boomerang-shaped growth, which prevails during life. Botanists do not
speak of such trees as possessing leaves, but "leaf-stalks dilated into
the form of a blade and usually with vertical edges, as in Australian
acacias." If one of these wattles is burnt to the ground, but yet retains
sufficient life to enable it to shoot from the charred stem, the new
growth will be of pinnate leaves, shortly to be abandoned for the
substitutes, which are of a form which checks transpiration and fits the
plant to survive in specially dry localities. Several of the species thus
equipped to withstand drought are extremely robust in districts where the
rainfall is prolific. There are no data available to support the theory
that such species in a wet district are more vigorous and attain larger
dimensions than representatives in drier and hotter localities. In her
distribution of the Australian national flower, Nature seems to be
"careless of the type," or rather regardless in respect of conditions of
climate.