Asystasia alba
Encyclopedia
Asystasia alba is a species of tropical
herb
in the Acanthaceae
family. It is endemic to Christmas Island
, an Australia
n territory in the north-eastern Indian Ocean
. Its specific epithet comes from the Latin
alba (white), referring to the colour of its flower
s.
are ovate, acuminate or acute, pale green in colour and usually bristly when young. The inflorescence
is 60–80 mm long, the flowers single or occasionally paired, the bract
s and bracteoles about 2 mm long and the pedicel
s 1.5–3 mm long. The corolla is white or violet, and the tube 14–18 mm long. The capsule is usually 2-seeded and about 26 mm long. The seeds are 4 mm long.
Asystasia alba is a variable species; it forms part of a species complex that includes A. australasica and A. oppositiflora, but differs from both of them in having single flowers at each axil.
up to about 200 m above sea level.
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
herb
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...
in the Acanthaceae
Acanthaceae
The family Acanthaceae is a taxon of dicotyledonous flowering plants containing almost 250 genera and about 2500 species....
family. It is endemic to Christmas Island
Christmas Island
The Territory of Christmas Island is a territory of Australia in the Indian Ocean. It is located northwest of the Western Australian city of Perth, south of the Indonesian capital, Jakarta, and ENE of the Cocos Islands....
, an Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
n territory in the north-eastern Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
. Its specific epithet comes from the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
alba (white), referring to the colour of its flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s.
Description
Asystasia alba is an erect woody herb, growing to 0.5–0.75 m in height. Its 30–140 mm long leavesLeaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
are ovate, acuminate or acute, pale green in colour and usually bristly when young. The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
is 60–80 mm long, the flowers single or occasionally paired, the bract
Bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
s and bracteoles about 2 mm long and the pedicel
Pedicel (botany)
A pedicel is a stem that attaches single flowers to the main stem of the inflorescence. It is the branches or stalks that hold each flower in an inflorescence that contains more than one flower....
s 1.5–3 mm long. The corolla is white or violet, and the tube 14–18 mm long. The capsule is usually 2-seeded and about 26 mm long. The seeds are 4 mm long.
Asystasia alba is a variable species; it forms part of a species complex that includes A. australasica and A. oppositiflora, but differs from both of them in having single flowers at each axil.
Distribution and habitat
Found only on Christmas Island, the plant occurs in cleared areas on the island’s terracesMarine terrace
A marine terrace, coastal terrace, raised beach or perched coastline is a relatively flat, horizontal or gently inclined surface of marine origin, mostly an old abrasion platform which has been lifted out of the sphere of wave activity . Thus it lies above or under the current sea level, depending...
up to about 200 m above sea level.