Cycas armstrongii
Encyclopedia
Cycas armstrongii is a species of cycad
in the genus Cycas
, native to Australia
, in the northwest of Northern Territory
from the Finniss River in the west to the Arnhem Highway
to the east.
The stems reach 3 m (rarely 6 m) tall, with a diameter of 5–11 cm. The leaves
are (very unusually for a cycad) deciduous
in the dry season
(though persistent if grown in moister situations), 55–90 cm long, slightly keeled or flat, pinnate with 100-220 leaflets; the leaflets densely orange-pubescent at first, then glossy bright green above, light green below, 5.5–14 cm long and 4.5–8 mm wide, angled forward at 40 degrees. Mature plants have around 50 leaves in the crown.
The female cones
open, with 13–22 cm long sporophyll
s with 2-4 ovules per sporophyll on a lanceolate triangular lamina
with an apical spine. The sarcotesta
has a yellow coating when ripe. The male cones are ovoid, orange, 11–20 cm long and 7.5–10 cm diameter, with upper half of cone drawn to a point.
The species is named after the plant collector John Francis Armstrong.
It is one of the most abundant cycads in the world, with a population estimate of over ten million. The conservation status is secure.
Cycad
Cycads are seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. The individual plants are either all male or all female . Cycads vary in size from having a trunk that is only a few centimeters...
in the genus Cycas
Cycas
Cycas is the type genus and the only genus currently recognised in the cycad family Cycadaceae. About 95 species are currently accepted. The best-known species is Cycas revoluta, widely cultivated under the name "Sago Palm" or "King Sago Palm" due to its palm-like appearance although it is not a...
, native to 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...
, in the northwest of Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
from the Finniss River in the west to the Arnhem Highway
Arnhem Highway
The Arnhem Highway is a 230 kilometre highway in the Northern Territory of Australia. It links the mining town of Jabiru, in Kakadu National Park, to the Stuart Highway 35 kilometres south of Darwin....
to the east.
The stems reach 3 m (rarely 6 m) tall, with a diameter of 5–11 cm. The leaves
Leaf
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 (very unusually for a cycad) deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
in the dry season
Dry season
The dry season is a term commonly used when describing the weather in the tropics. The weather in the tropics is dominated by the tropical rain belt, which oscillates from the northern to the southern tropics over the course of the year...
(though persistent if grown in moister situations), 55–90 cm long, slightly keeled or flat, pinnate with 100-220 leaflets; the leaflets densely orange-pubescent at first, then glossy bright green above, light green below, 5.5–14 cm long and 4.5–8 mm wide, angled forward at 40 degrees. Mature plants have around 50 leaves in the crown.
The female cones
Strobilus
A strobilus is a structure present on many land plant species consisting of sporangia-bearing structures densely aggregated along a stem. Strobili are often called cones, but many botanists restrict the use of the term cone to the woody seed strobili of conifers...
open, with 13–22 cm long sporophyll
Sporophyll
A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls bear either megasporangia , or microsporangia...
s with 2-4 ovules per sporophyll on a lanceolate triangular lamina
Leaf
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....
with an apical spine. The sarcotesta
Sarcotesta
The sarcotesta is the outermost fleshy covering of Cycad seeds. Below this layer is usually the sclerotesta, the coating that makes direct contact with the cycad seed. In some species, however, there is an intermediate layer that is thought to be used in water retention and storage....
has a yellow coating when ripe. The male cones are ovoid, orange, 11–20 cm long and 7.5–10 cm diameter, with upper half of cone drawn to a point.
The species is named after the plant collector John Francis Armstrong.
Ecology
Annual grass fires are common in its natural habitats. The species is extremely fire tolerant, and the usually early spring fires initiate a profusion of new leaf growth in the plants, thus the common name, fire fern.It is one of the most abundant cycads in the world, with a population estimate of over ten million. The conservation status is secure.