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A Fern which Changed Australian History
Over a large area of inland eastern Australia the semi-aquatic fern, Marsilea drummondii may be found. It grows in swamps and bogs, billabongs, slow-flowing streams and in areas of temporary flooding. It grows in hot and dry inland areas when rain causes temporary filling of water holes and road-side puddles.
At first sight it may be mistaken for clover. Its common name is Nardoo, and is a fern superficially resembling clover - a four-leaf clover. Nardoo belongs to the genus Marsilea. There are seven species of Marsilea occurring in Australia and about sixty world wide. Most are not rare but are often overlooked because of their resemblance to clover. M.drummondii is the most common species in eastern Australia.
The genus is named after Count Luigi Ferdinando Marsigli (1656-1730), an Italian botanist, and the specific name is for James Drummond (1784-1863), first Government Botanist of Western Australia.
A few years ago, following particularly good rain in areas of central western New South Wales, there was much flooding. On two trips to Adelaide, in November and February, I found water lying in many places beside the Barrier Highway. Marsilea was not scarce and in places could be observed in massive patches in the water even while driving past at 100 km/h. Thick patches were present in many places from 40 km past Cobar to 43 km west of Wilcannia.
Characteristics of Marsilea
These are aquatic or sub-aquatic ferns and consist of two pairs of opposite leaves forming a circular blade, each leaf widely or narrowly wedge-shaped and capable of floating on the surface of water. They may be mistaken for four-leaved clovers because of the pattern of the four leaf blades. A clue to these being ferns is seen in the unfolding of the new fronds. Careful examination shows the young leaves to be coiled and these unfurl like a typical fern crozier or fiddlehead.
On water edges the leaves often form a tangled mass and are held semi-vertically out of the water. In deep water they either float on the surface or are held erect above the surface. Leaflets are generally covered with fine hairs. These are more abundant in specimens growing out of water. The hairs resist drying in the atmosphere and probably assist flotation. Leaflets growing out of water also exhibit "sleep movement". This interesting phenomenon is the furling of leaflets when the intensity of light becomes low. Hence they tend to "close up" in the evening and on very dull days.
Nut-like structures on stalks develop from the rhizome, which grows in the mud. These "nuts" develop from modified leaves and it is within them that spores develop. They also contain a starchy structure which, on maturity, expands by the absorption of water.
David Jones states, when describing this family, Marsileaceae and a related family, Azollaceae, "These are the only true ferns to produce separate male and female prothalli. It is this degree of specialisation that makes the genus the most advanced of living ferns".
Prothalli are the structures which develop from fern spores and produce eggs and sperm which ultimately produce the new generation fernlings. In all other ferns the individual prothallus produces both eggs and sperm but here a prothallus will produce only one or the other.
Beri-beri is a disease first described by Jacobus Bintius, a doctor who graduated in 1614 and commenced practice in Leyden. He was also an ardent student of botany and natural history.
He found medical practice poorly paid and eventually joined the East India Company and migrated to Batavia in 1627 where he became Attorney General. Here, in his spare time, he observes the flora and fauna and wrote four books before he died in 1631 at the age of 39.
Most people died young in Batavia due to 'the fever' - malaria. It was most unhealthy, tropical with a high rainfall and poor drainage. The city drains were always loaded with breeding mosquitoes. His books described the fauna, flora, fish and medicine in the East Indies. In Medicine Indorum we find the first description of beri-beri.
"This is a type of paralysis which the natives call beri-beri. Beri-beri means sheep......with knees shaking, and their legs raised up, (they) walk like sheep. It is a kind of paralysis, or rather Tremor for it penetrates the motion and sensation of the hands and feet indeed sometimes the whole body and produces tremors....There is a lassitude of the whole body."
So far his observations were accurate but when he got onto the cause he went wrong - assuming rather than investigating. He stated: "The especial cause of the disease is the dense and sticky phlegmatic humor, which in the nocturnal time, particularly in the rainy season.....corrupt the nerves...". We now know that the cause is vitamin B1 deficiency. Of course vitamins were unknown until early this century. The symptoms of beri-beri are:
|*||Loss of appetite, which causes the disease to progress as thiamine is absorbed from food. Pleural transduate (a serous effusion into the airways of the lung).
|*||Chyne Stokes respiration or periodic breathing (breathing which gradually increases in depth and then gradually diminishes to stop for up to a couple of minutes before recommencing the cycle again). This type of breathing can be normal in some young or old people but may denote grave disease. Here it is caused by myocardial weakness and cardiac insufficiency (weakness of the heart muscle and heart enlargement denoting cardiac decompensation or partial heart failure).
|*||Generalised oedema (collection of serous fluid in the tissues) due to cardiac failure and hypoproteinaemia (low serum protein due to failing kidney function).
|*||Palpitation (consciousness of the heart beat which sometimes may be fast) due to cardiac failure.
|*||Polyneuritis manifest by weakness and paraplegia (partial or complete paralysis of the lower limbs caused by disease of the nervous system), loss of tendon reflexes, slight peripheral sensory loss and a high-stepping gait associated with foot drop - hence the reference to sheep.
Formation of these nut-like structures chiefly takes place as the ponds dry up and rarely occurs in wet conditions. Maturation is slow and takes up to three years. This mechanism ensures that the spores can resist desiccation and is particularly suitable to inland areas of the continent and in areas of uncertain rain.
Nardoo as Food
The advent of rain commences an interesting series of events. The starchy material absorbs water and swells into a gelatinous material which ultimately bursts the structure liberating the spores. This is the useful part of the sporocarp for food and the nut-like sporocarps were gathered by Aborigines for this purpose. The formation and resistance of the sporocarp to desiccation and its abundance in good years has made it a good Aboriginal food.
The sporocarps were ground to a flour-like substance and mixed with copious amounts of water to form a thin paste. This was eaten raw or cooked into thin cakes.
The sporocarps contain the enzyme thiaminase which destroys vitamin B1 and if taken continuously results in beri-beri. The preparation with water washes away or dilutes the enzyme, minimising its effect. The sporocarps are quite small, 4-9 mm in length and about 3 mm in width so that it must take a full day to collect enough to make a meagre meal.
Thiaminase is found in a couple of other fern genera, Cheilanthes (the Resurrection Ferns) and Pteridium (the Brackens). Strangely enough it is also found in the flesh of raw carp fish. It has been found that cholinesterase levels are raised in the tissues of people with low thiamine. Cholinesterase acts in the nerve synapses and the raised levels may account for the interference to the peripheral nervous system in sufferers from beri-beri.
Thiamine or, vitamin B1, is essential in the body for the metabolism of carbohydrates (sugars) and the normal function of nervous and heart tissue. But is necessary only in a very small amount. The daily requirement is 1-1.5 mg daily or about an amount the size of the head of a pin. Normally it is obtained from food being high in yeast, whole grains, nuts legumes, potatoes, egg yoke and meat. In grains and seeds it occurs in the germ or embryonic tissue and is stable to cooking unless an alkali is added.
The addition of baking powder, which is alkaline, therefore destroys the vitamin in cakes and wholemeal bread. It is not present in polished rice or white flour. In the process of making white flour for cooking and bread the traditional method removes the wheat germ and consequently the thiamine. Wheat germ also contains a fat which is liable to rancidity and attracts weevils. Its removal therefore makes the flour last longer.
In the fermentation of alcohol from glucose yeast causes a chain reaction of many stages. In one stage vitamin B1 combines with a chemical supplied by the yeast, pyrophosphate which acts like a catalyst. This substance also occurs in the brain of humans. In vitamin B1 deficiency the lactic acid level in the brain rises and interferes with its normal function.
Lactic acid normally results from muscle activity and is eliminated in the kidney. It is the cause of pain in the legs when you run too far too fast. Too much lactic acid is then produced for the blood vessels to convey to the kidneys fast enough to maintain the normal level in the blood. Faster removal occurs after training to increase exercise tolerance such as in athletes.
Beri-beri was a common disease in the East where a large proportion of the population subsisted upon rice as the predominant food. Most of these people refused to eat any but polished rice where, unfortunately, thiamine was removed with the natural rice dust and grain germ.
Other foods containing thiamine were not eaten in large enough quantities being either unobtainable or unaffordable. Even after the cause of beri-beri was discovered, there was great resistance to eating unpolished rice.
Nardoo and the Burke and Wills Tragedy
There are many notes on the use of nardoo as food by Aborigines in the journals of the early explorers of Australia. But perhaps the most graphic and famous are those recorded by Wills towards the end of the fatal Burke and Wills Exploring Expedition of 1860.
When they had no food left they were fed nardoo by the Aborigines and collected their own to try to overcome starvation. They made use of this food but did not prepare it properly, developed beri-beri and died from the combined effects of this disease and starvation.
At Cooper Creek on June 3, 1861 Wills wrote... "The fish being disposed of, next came a supply of nardoo cake and water, until I was so full as to be unable to eat more; when Pitchery, allowing me a short time to recover myself, fetched a large bowl of the raw nardoo flour, mixed to a thin paste, a most insinuating article, and in that they appear to esteem a great delicacy...."
This fish and nardoo was given to them by the Aborigines. Wills actually describes here how the Aborigines prepared the flour in a thin paste but unfortunately did not follow the recipe. The following extracts are from the journal of W.J. Wills, found after his death on Cooper Creek. The comments in this journal graphically describe the symptoms in the final few days of a man dying from beri-beri.
|"Wills actually describes here how the Aborigines prepared the flour in a thin paste but unfortunately did not follow the recipe. "
On Wednesday, June 12, 1861 he wrote.... "King out collecting nardoo. Mr Bourke and I at home, pounding and cleaning. I still feel myself, if anything, weaker in the legs, although the nardoo appears to be more thoroughly digested."
June 14.... "I feel weaker than ever, and both Mr. B. and King are beginning to feel very unsteady in the legs."
June 15.... "I have determined to chew tobacco and eat less nardoo, in hopes that it may induce some change in the system. I have never yet recovered from constipation, the effect of which is exceedingly painful."
June 20...."Finding the sun come out pretty warm towards noon, I took a spongeing all over, but it seemed to do little good beyond the cleaning effects, for my weakness is so great that I could not do it with proper expedition. I cannot understand this nardoo at all; it certainly will not agree with me in any form. We are now reduced to it alone, and we manage to get four to five pounds per day between us."
June 23.... "All hands at home. I am so weak as to be incapable of crawling out of the Mia Mia."
June 28, the last entry in his journal.... "Nothing now but the greatest good luck can save any of us; and as for myself, I may live four or five days if the weather continues warm. My pulse is at forty-eight, and very weak, and my legs and arms are nearly skin and bone. I can only look out, like Mr. Micawber, 6 for something to turn up. Starvation on nardoo is by no means very unpleasant, but for the weakness one feels, and the utter inability to move oneself, for as far as the appetite is concerned, it gives me the greatest satis faction. Certainly fat and sugar would be more to one's taste; in fact, those seem to me to be the great stand-by for one in this extraordinary continent; not that I mean to depreciate the farinaceous food, but the want of sugar and fat in all substances obtainable here is so great that they become almost valueless to us as articles of food, without the addition of something else."
He died within the next four days and Bourke died on June 26/7. In spite of starvation the fern was primarily the killer!
Why does this fern contains this toxic chemical? Does it benefit the plant or is it purely a fortuitous metabolite?
From the October-December 2000 issue of the newsletter of the Far North Coast Group of the Australian Plants Society (NSW).
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