Cycas armstrongii

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Figure 1. Large branching specimen, 150km south-east of Darwin.

Cycas armstrongii was named for a gardener from Kew who was a keen collector and resided in the Northern Territory. In areas of the far north of Western Australia and indeed south-west of Darwin near the Western Australia/Northern Territory border it is known as Cycas lanepoolei (C. Gardner). The late J.R. Maconochie stated that this name was synonymous and that C. armstrongii had priority. The form C. lane-poolei extends into the coastal ranges of the top end of Western Australia. Typical of all the family, the plants are dioecious and in this species, also deciduous, generally after April.

This cycad grows to approximately 4.0 m and if unburnt caudices can be observed the colour is charcoal grey, very rough and up to 15cm in diameter.


Figure 2. Emerging leaves and mature seeds.

Most mature plants carry on average approximately 50 fronds being a little over 1 m in length, the pinnae pea-green on the surface and mottled with yellow on underside. Each of the adjacent leaf pinnae having prominent midrib vein visible above and below. The male cone emerges from the apex of the plants and is on average 20cm in length, oval but pointed at the apex. The colour is deep rusty hue and composed of hundreds of scales arranged somewhat in a spiral. At first, tightly closed, but opening later to eject dust-like spores. The female forms a cone at the apex also. The sporophylls enclosing many small ovoid green seed. Later this 'cone' opens fully and the sporophylls arch outward and hang pendant from the plant's crown. Approximately 4 ovules to each sporophyll which is flattened, pubescent and has a triangular spear head shape at the end of each. Thin basal stem lobes are below the ovules The pendant fruit being 20-40cm across and yellowish/brown when ripe. Because of certain familiar aspects this species has earlier been confused with the east coast Cycas media. However Cycas armstrongii has a much narrower caudex, and Cycas media is seldom deciduous naturally. This particular species along with a sister species Cycas calcicola is much maligned in the territory and suffers from the annual burn off which was part of the aboriginal way of life, but is now continued by many cattlemen across our Top End. Fires natural or man-produced generally blacken the caudices, and destroy much of the ripe seed. However the resulting new fronds carry a very powerful defence mechanism in the poison Cycasin which affects all the cattlemen's herds. These, as

stated elsewhere  are mostly scrubber, or wild station cattle.

Introduction to Australian Cycas), are mostly scrubber, or wild station cattle. The rejuvenating new fronds of both Cycas armstrongii and Cycas calcicola are referred to locally as "fire-fern". Cycas armstrongii occurs in open forests and generally in sandy loam vicinities. However, in various localities it can be found in dense stands near granite outcrops. Quite often the populations of C. armstrongii spill over into territories where C. calcicola grows and at least one researcher believes he has found obvious hybrids between the two species.

File:Cycas images/armstrongii2-01.jpg
Figure 3. Cultivated specimen.
Figure 4. C. armstrongii in habitat.
Figure 5. C. armstrongii southeast of Darwin.

center

Figure 6. Male cone of C. armstrongii.


Contributed by:

L. P. Butt (from Palms & Cycads No. 27, Apr-Jun 1990)

External Links:

Cycad Pages, IUCN, JSTOR, Trebrown

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