''Asystasia alba'' is a species of
tropical
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
herb in the family
Acanthaceae
Acanthaceae is a family (the acanthus family) of dicotyledonous flowering plants containing almost 250 genera and about 2500 species. Most are tropical herbs, shrubs, or twining vines; some are epiphytes. Only a few species are distributed in tem ...
. It is
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...
to
Christmas Island
Christmas Island, officially the Territory of Christmas Island, is an Australian external territory comprising the island of the same name. It is located in the Indian Ocean, around south of Java and Sumatra and around north-west of the ...
, an
Australian territory in the north-eastern
Indian Ocean
The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...
. Its
specific epithet comes 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 ...
''alba'' (white), referring to the colour of its
flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechani ...
s.
Description
''Asystasia alba'' is an erect woody herb, growing to 0.5–0.75 m in height. Its 30–140 mm long
leaves are ovate, acuminate or acute, pale green in colour and usually bristly when young. The
inflorescence
An inflorescence is a group or cluster of flowers arranged on a Plant stem, stem that is composed of a main branch or a complicated arrangement of branches. Morphology (biology), Morphologically, it is the modified part of the shoot of sperma ...
is 60–80 mm long, the flowers single or occasionally paired, the
bracts and bracteoles about 2 mm long and the
pedicels 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 terraces up to about 200 m above sea level.[Flora of Australia Online.]
References
Notes
Sources
*
*
alba
''Alba'' ( , ) is the Scottish Gaelic name for Scotland. It is also, in English language historiography, used to refer to the polity of Picts and Scots united in the ninth century as the Kingdom of Alba, until it developed into the Kingdom ...
Endemic flora of Christmas Island
Lamiales of Australia
Plants described in 1906
Taxa named by Henry Nicholas Ridley
{{Acanthaceae-stub