''Isotoma petraea'', commonly known as rock isotome, is a small, herbaceous plant in the family '' Campanulaceae'' occurring in arid regions of Australia. It has single, purplish-blue flowers on smooth, slender branches from February to November.

Description

''Isotoma petraea'' is an erect, spreading, perennial or annual herbaceous plant with smooth branches that typically grows to a height of . The smooth leaves are narrowly egg-shaped to elliptic, long, wide,

petiolate Petiole may refer to: *Petiole (botany), the stalk of a leaf, attaching the blade to the stem *Petiole (insect anatomy) In entomology, petiole is the technical term for the narrow waist of some hymenopteran insects, especially ants, bees, a ...

on lower sections

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

toward the branch apex, sharply lobed, unevenly spaced teeth and ending in a point. The blue-purplish flowers are borne singly on a wiry peduncle long. The calyces are narrow-triangular, pointed, long, corolla is mostly white and may have a flush of purplish-blue, a light green floral tube long with prominent veins. The smooth petals are lance-oblong shaped long and tapering sharply to a point. The fruit are rounded, slightly ribbed and long. Flowering occurs mostly in summer.

Taxonomy and naming

This species was first formally described in 1853 by

Ferdinand von Mueller Baron Sir Ferdinand Jacob Heinrich von Mueller, (german: Müller; 30 June 1825 – 10 October 1896) was a German-Australian physician, geographer, and most notably, a botanist. He was appointed government botanist for the then colony of Vict ...

and the description was published in ''Linnaea: ein Journal für die Botanik in ihrem ganzen Umfange, oder Beiträge zur Pflanzenkunde''. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

(''petraea'') is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''petraeus'' meaning "growing amongst rocks".

Distribution and habitat

It is found on breakways, among rocky outcrops and in rock crevices in the Mid West, Wheatbelt and Goldfields-Esperance regions of Western Australia where it grows in shallow sandy soils over

granite Granite () is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies undergro ...

.In

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

it grows west of Wilcannia mostly on slopes and rocky locations on shallow granite based soils. In

South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...

it is a widespread species growing in rocky locations.

References

{{Taxonbar, from=Q15603754 petraea Flora of Australia Plants described in 1853 Taxa named by Ferdinand von Mueller