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Rostellularia adscendens (R.Br.) R.M.Barker 1986
pronounced: rohs-tell-yoo-LAIR-ree-uh ad-SKEN-denz
(Acanthaceae – the black-eyed Susan family)
synonym: Justicia adscendens R.Br. 1810
common name: Pink Tongues
Rostellularia is from the Latin rostellum, a little beak;adscendens is Latin for ‘climbing up’. There is some uncertainty about the taxonomy of this plant: the current Plant List of Kew Gardens lists it as ‘an unresolved name’.
This little ascending herb is a native of Australia, but not endemic to this country. It is also found in tropical and sub-tropical America and Africa, Madagascar, Indonesia, and PNG. In Australia it occurs across the northern part of the country, and southwards down the east coast to central NSW. It can also be found in northern South Australia and the Pilbara region of Western Australia.
This plant was collected by Banks and Solander at the Endeavour River in 1770. It was named by Robert Brown in his book Prodomus Floræ Novæ Hollandiæ∗ , 1810. Brown (1773–1858) was a Scottish botanist who accompanied Matthew Flinders on his circumnavigation of Australia, and named many Australian native plants. Before joining Flinders in the Investigator, Brown had studied the plants in Sir Joseph Banks’s collections, and the voyage undoubtedly helped him to develop the powers of acute observation and intense application which gained him the dominant position he held in the scientific world in the first half of the 19th century. He made extensive collections during Flinders’ coastal surveys, although the major part of his material from the south coast was lost in the wreck of the Porpoise in 1803. He discovered many plants that he thought were unknown; but, after he returned to England, he found that La Billardière had described many of them in his Novæ Hollandiæ Plantæ Specimen† (1804 – 1806). Brown went on to become a notable botanist; but he is best remembered for his discovery of Brownian Motion in 1827. There is not the space here to describe this motion adequately: Brown was studying pollen particles of Clarkia pulchella in water under the microscope. He then observed minute particles, ejected by the pollen grains, executing a jittery motion. By repeating the experiment with particles of inorganic matter, he was able to rule out that the motion was life-related, although the origin of the motion was yet to be explained. That was done later by others, but the motion was named after Brown.
He gave this plant the name Justicia adscendens, and it was transferred to the Rostellularia genus in 1986. This transfer is not universally accepted.
The plant grows to between 5 and 50 cm high, becoming a bush at the higher end of the range, and is found along streams or in rocky areas in woodland. The plants photographed were under some Townsville Wattle trees near the service road leading to the Picnic Bay water tower. They were very small, and hard to spot when growing among grasses and other herbs. The species has been studied in some depth by R.M. Barker (Flora of Australia, 1999) who divides it into 2 subspecies and some 7 varieties.
The twigs are longitudinally grooved and clothed in hairs. The leaves are shortly petiolate, the petioles about 5–7 mm long. The leaf blades are variable in size, some 6–25 mm long by 2–15 mm wide. There are no stipules. The flower spikes, of densely overlapping bracts, are 1–5 cm long, dense, sometimes interrupted at the base. The individual flowers have a 5-lobed calyx, 4 of the lobes large and 1 small. The corolla is 4–7 mm long: there is an upper lip with one lobe and a lower lip with 3 small lobes at the apex, each with a thickened swelling. The anther sacs are more-or-less separate from one another, more-or-less growing above each other with the lower anther sac tailed. The style is sparsely hairy, at least in the lower half; the stigma is minutely 2-lobed; the ovary is seated on a lobed cup-shaped disk. The flower colours vary according to the subspecies or variety, and may be blue, purple, violet, pink, or white. The seed capsule is non-fleshy and elastically dehiscent, about 3–6 mm long with between ⅔ and ¾ of the capsule enclosed by the calyx lobes. The capsule is hairy on the outer surface, at least towards the apex. There are 4 seeds per fruit. They are flattened, and more-or-less circular, and not conspicuously hairy.
This is a food plant for the Blue Angus butterfly, Junonia orithya.
∗ Introduction to the Flora of New Holland
† An Example of a New Holland Plant
Photographs taken at Picnic Bay 2011
Page last updated 24th June 2018