Today’s image brings us a close-up view of Homoranthus papillatus, or mouse bush. Unless you’re planning a trip to Queensland in Australia anytime soon, a photograph like this may be one of your few (or only) encounters with this vulnerable and endemic species.
Homoranthus was first described in 1836. It is a member of the Myrtaceae (myrtle family). All of the approximately 23 species in this genus are endemic to Australia. Mouse bush is classified as vulnerable in Australia by the NCA (Nature Conservation Act), and, like many other members of the genus, dwindling in abundance. The species is also uncommon in horticulture.
The native distribution of Homoranthus papillatus is restricted to specific areas of Queensland’s Girraween National Park. Trampling by park visitors is the main threat to the survival of this small shrub, because of its tendency to grow on rocks or pavement areas with frequent human traffic. Altered fire regimes have also been suggested as a threat to the species.
Mouse bush is a spreading but compact shrub, reaching a height of 1m (~3 ft.). Its common name alludes to the strong odour associated with these plants, which is asserted to smell of mice. Unlike most species of the Myrtaceae, all species of Homoranthus have oppositely-arranged leaves. These leaves are roughly 1cm in length and triangular in cross-section. The long protrusions extending from the flowers are the styles; these stem from the ovary and support the stigma at their tip. Long protruding styles are characteristic of the genus, a trait shared with some (though certainly not all) members of the family. The other parts of these slender flowers include the greenish base (which is a distinctly five-ribbed calyx tube), five small translucent petals, and ten red staminodes.
The specific epithet, papillatus, is likely derived from the presence of papillae on the leaves. Papillae are small fleshy projections from the surface of a plant, only visible in the case of mouse bush with a magnifier of some kind. Homoranthus montanus is a species similar in appearance to Homoranthus papillatus, but doesn’t grow in Girraween National Park, lacks papillae, and has a taller growth form.