Cycas OzIntro

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Figure 1. C. cairnsiana in habitat, Petford.

Contents

Introduction:

Many species of the genus Cycas (pronounced sigh-cas), the solitary member within the family cycadaceae (pronounced sigh-cad-ace-ee-ay), have now been recognized in Australia where once it was thought that only Cycas media flourished. Two other species were mentioned in early papers: Cycas cairnsiana and C. normanbyana. No real clarification existed. Since then, owing to work done by a senior botanist in the Northern Territory, it is known that many other species do exist in Australia.

Evolution:

The genus Cycas has such pronounced primitive features that early botanists theorized that it was the missing link connecting the pteridosperms or cycadofilicales of the Devonian Era with Zamiaceae fossils which occured in the Mesozoic age, a much later period. Even though the genus has very primitive features, (for example central fronds rising circinately from the apex and the female not formimg a cone) Dr. L.A.S. Johnson stated that the genus could hardly have risen from a period before the Zamiaceae since the genus distinguishing single vein stem in the pinnae could not have given rise to the frond condition of living zamiads. Another remarkable thing about condition of the seed arrangement of Cycas is that the seeds form on the margins of a brown-furred, frondlike megasporophyll issuing from the crown of the trunk and in the Australian species hanging pendant between the bases of the fronds. This last feature is definitely similar to what we know of the pteridosperms of the Paleozoic age. Perhaps Cycas can be classified as the most primitive genus alive today. From illustrations given by Professor Chamberlain in 1919, the primitive seed ferns were also very similar to this.


Distribution:

Cycas is a far-flung genus of plants occur ring in Japan, China, Philippines, Taiwan, the Indian sub-continent, Sri Lanka, South East Asia, Madagascar, Malesia, New Guinea, the western Pacific and northern and north-eastern Australia. However, from incomplete botanical study it appears that Australia has more species than any other country.

Present Status:

Botanical study of Cycadaceae is still in progress here in Australia and although incomplete, the amount of progress so far is remarkable when one considers that very few botanists are studying the entire Cycadale group with any thought in mind of merit to the plants. Rather, study is being carried out to determine the peculiarities of the toxins the cycads contain, and their effects on primary livestock.

After discussion with farmers, in particular the man who grazes cattle, it emerges that most of the Zamiaceae are inaccessible to stock at normal times. Most zamiads are either too formidable in leaf structure, or their seed is enclosed in heavy cones. Also many of them have protective spines while in cone formation.

However the Cycadaceae present a different picture because of the peculiar manner of their seed hanging exposed from between the leaf fronds at the apex of the plant's trunk. Also in the case of Cycas the group of tender young new fronds emerge from time to time in their circinate fashion. This presents an attractive soft repast to wandering 'scrubbers' or straying cattle who immediately eat this and develop a ricketts type of complaint or partial paralysis of the hind legs. Because they are straying stock they die of starvation rather than from the plant's toxic properties. I have discussed the situation regarding stock with many farmers and even those that totally disregard the plants as having any use will admit that most stock fatalities occur when drought conditions prevail and fires have burnt off an area leaving only blackened caudices, which triggers new growth.

However because of such stock losses reports to primary industry authorities are made, which result in certain Australian authorities declaring the indigenous family as noxious.

Most other countries throughout the world realize their real value as marvellous botanical specimens with good commercial possibilities. South Africa and America have raised protective laws by declaring their cycads as plants in danger of extinction. Further, could I pose the question, "just how many indigenous plants have been declared noxious weeds in their own country?." Professor Chamberlain stated in 1919, with reference to Cycads, "it is nothing short of vandalism to destroy by arsenic poisoning, plants of scientific importance." On the home garden and landscaping front, the extreme hardiness and palmlike beauty of the cycad family makes them ideal subjects for tub culture or for planned garden landscaping. As greater knowledge of the family is gained the existing law may change to the benefit of all concerned. To illustrate the degree of lack of knowledge of these plants at authoritarian level, the reference to the noxious plant by authorities is as "Zamia", a genus which is not even indigenous to Australia. It is found much farther afield in Florida, Central and South America.

Contributed by:

L. P. Butt from Palms & Cycads No. 27, April-June 1990.

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