''Cycas armstrongii'' is a species of

cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...

in the genus ''

Cycas ''Cycas'' is a genus of plants belonging to a very ancient lineage, the Cycadophyta, which are not closely related to palms, ferns, trees or any other modern group of plants. They are evergreen perennials which achieved their maximum diversity in ...

'', endemic to

Northern Territory The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an states and territories of Australia, Australian territory in the central and central northern regions of Australia. The Northern Territory ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. It is found from the Finniss River in the west to the

Arnhem Highway The Arnhem Highway is a 227—kilometre highway in the Northern Territory of Australia. It links the mining town of Jabiru, in Kakadu National Park, to the Stuart Highway at a point 35 kilometres south of Darwin. Upgrades The Northern Aus ...

in the east, north of Pine Creek. It also occurs on the

Tiwi Islands The Tiwi Islands ( tiw, Ratuati Irara meaning "two islands") are part of the Northern Territory, Australia, to the north of Darwin adjoining the Timor Sea. They comprise Melville Island, Bathurst Island, and nine smaller uninhabited islands, wi ...

and the

Cobourg Peninsula The Cobourg Peninsula is located east of Darwin in the Northern Territory, Australia. It is deeply indented with coves and bays, covers a land area of about , and is virtually uninhabited with a population ranging from about 20 to 30 in five ...

The stems reach 3 m (rarely 6 m) tall, with a diameter of 5–11 cm. The

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

are (very unusually for a cycad)

deciduous In the fields of horticulture and Botany, the term ''deciduous'' () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, aft ...

in the

dry season The dry season is a yearly period of low rainfall, especially in the tropics. The weather in the tropics is dominated by the tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year. The te ...

(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 A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex. A cone is formed by a set of line segments, half-lines, or lines conn ...

open, with 13–22 cm long

sporophyll A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls (whether they are microphylls or megaphylls) bear either megasporangia and thus are called megasporophylls, or mi ...

s with 2-4 ovules per sporophyll on a lanceolate triangular

lamina Lamina may refer to: Science and technology * Planar lamina, a two-dimensional planar closed surface with mass and density, in mathematics * Laminar flow, (or streamline flow) occurs when a fluid flows in parallel layers, with no disruption betwee ...

with an apical spine. The

sarcotesta The sarcotesta is a fleshy seedcoat, a type of testa. Examples of seeds with a sarcotesta are pomegranate and some cycad seeds. The sarcotesta of pomegranate seeds consists of epidermal cells derived from the integument In biology, an integu ...

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. Fruiting: March to September. The species is named after the plant collector John Francis Armstrong (d. 1847), a

Kew Gardens Kew Gardens is a botanical garden, botanic garden in southwest London that houses the "largest and most diverse botany, botanical and mycology, mycological collections in the world". Founded in 1840, from the exotic garden at Kew Park, its li ...

plant collector, who was based at

Port Essington Port Essington is an inlet and historic site located on the Cobourg Peninsula in the Garig Gunak Barlu National Park in Australia's Northern Territory. It was the site of an early attempt at British settlement, but now exists only as a remote ...

on the

Habitat

This cycad is common in open forest and woodland around the Darwin region, north of Pine Creek. It usually grows on well-drained sandy and lateritic soils. It may be confused with Cycas maconochiei.

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.

References

Cycad Pages: ''Cycas armstrongii''
{{Taxonbar, from=Q159799 armstrongii Cycadophyta of Australia Endemic flora of Australia Flora of the Northern Territory Vulnerable flora of Australia