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.
Human beings, and occasionally animals lower in the scale, deviate distressingly in their conduct from the general. Plants, too, though lacking the organ of brain, are subject to aberrations of foliage almost as fantastical as the mental bent which in man is displayed by the sticking of straws in the hair. “Phyllomania” is the recognised term for this waywardness. One of the trees of this locality, the raroo (CAREYA AUSTRALIS), seems singularly prone to the infirmity, for without apparent cause it abandons habitual ways and clothes its trunk and branches with huge rosettes of small, slight, and ineffective leaves, evidence, probably, of vital degeneration.