The Durban Botanical Gardens hosts several portions of the original plant, salvaged apparently shortly before being carted off for firewood by the indigenous population; these have now developed into magnificent prize specimens. Fortunately, E. woodii produces offsets quite readily and careful vegetative propagation has resulted in a fair number (500?) of plants being established in major botanical gardens and private collections throughout the world. Since all these plants are male, it is impossible to propagate the species from seed. But two new approaches hold hope for the future.

The first approach is being adopted by Cynthia Giddy* at her Umlaas Road nursery and has been described by D.C. Speirs. Pollen from male cones of the existing E. woodii plants is used to fertilize E. natalensis, the species which seems to be most closely related. Females from this hybrid generation (F₁, 5O% E. woodii) are back-crossed with more E. woodii pollen to give another generation a little closer to pure E. woodii (F₂, 75% E. woodii). The process is repeated until an almost pure population is established--e.g., the F₅ generation would be 97% E. woodii. The disadvantage, of course, lies in the length of time from one generation to another; assuming 12 years for each batch to come to maturity, the 5-generation process takes 60 years.

A second plan of action follows from the rather unusual, but now well-documented evidence that sex changes can and do occur in cycads. In 1967 Menninger described two instances of sex reversal. In Cycas circinalis one plant changed from female to male after severe physical damage, while the opposite change occurred when another plant was badly frost damaged. The most authoritative report of sex change was presented by Van Wyk and Claassen from the Department of Botany, University of Pretoria, in 1981. Dr. Claassen obtained several specimens of E. umbeluziensis which were transplanted into her Pretoria garden in December 1967; one of these plants produced a male cone in 1970 but a female cone several years later. The reversal might be associated with either the trauma of being transplanted or a sudden cold spell in August 1972. (See also the article "Sex change in specimen of Cycas revoluta" elsewhere in this edition.) Other, less well-documented instances of sex-reversal in mature cycad plants are not uncommon. Mr. Koeleman of Magaliesberg Research Nursery, for instance, knows of a female Zamia (7) which produced an offshoot with a male cone. Nearly all these cases have one thing in common and that is some traumatic incident like physical damage or severe cold weather prior to the sex reversal.

The sex expression of plants appears to be a function of hormonal control; there seems to be evidence that dioecious plants (male and female reproductive organs on separate plants) are potentially bisexual and that a delicate internal hormonal balance results in one sex "over-riding" the other. A traumatic incident might, therefore, act by temporarily upsetting this balance which is later restored in a way which leads to the opposite sexual character being manifested. Another pointer in this direction is the fact that a variety of artificially applied chemical substances has been shown to affect the sexual expression of a significant number of different plants. Jan Ceuns, working in Belgium, believes that the class of chemicals known as the steroid hormones might be a major key to the sex expression lock. All this indicates that it might be possible to "create" a female E. woodii by either a physical shock or a controlled chemical process.

However, no-one would suggest that we start putting our precious E. woodii plants in the deep freeze or spray them with random chemical cocktails. What is needed is a large uniform population of small plants to experiment with and I believe the clue here lies in tissue culture techniques.

Various scientists have looked into the feasibility of taking small tissue portions from different parts of cycad plants and "cloning" these in test-tube culture media to give large numbers of identical progeny. Professor Paola de Luca and his team in Naples, the research unit of Fairchild Tropical Garden in Florida, and Mr. Koeleman at Hartbeeshoek have all been working along these lines. Producing a mass of callus material in culture seems to be quite easy; the difficult bit is in "persuading" the callus to form roots and shoots and develop into a plantlet which can later be moved into a normal soil environment. Time and patience will undoubtedly perfect this technique.

It is my hope to work on these techniques so that we can mass-produce sufficient E. woodii material for a properly-controlled experiment. The experiment itself will comprise a series of physical and chemical regimes, one of which I believe should lead to the creation of a 100% pure, female E. woodii. The success of this Adam and Eve story would be fantastic news to growers and conservationists alike.

REFERENCES

1. 'P. de Luca et al.: "In vitro spermatogenesis of Encephalartos", Caryologia 32, 1979.
2. P. de Luca et al.: "Regeneration in megagametophyres of cycads", Giorn. Bot. Ital. 113, 1979.
3. J. Geuns: "Plant steroid hormones--what are they and what do they do?", Trans. Biochem. Sci. 7, 1982.
4. J. Geuns: "Steroid hormones and plant growth and development", Phytochemistry 17, 1978.
5. A. Koeleman: Private communication, 1984.
6. A. Koeleman & S. Small: "A note on callus formation by stem and root tissue of some Encephalartos species", S. Air. S. Bot. 1, 1982.
7. E.A. Menninger: "Fantastic Trees", Viking Press, New York (1967); reprinted by Horticultural Books, Inc., Florida (1975).
8. K. Norstog: "Induction of apogamy in megagametophytes of Zamia integrifolia", Am. J. Bot. 52, 1965.
9. K. Norstog & E. Rhamstine: "Isolation and culture of haploid and diploid cycad tissues", Phytomorph. 17, 1967.
10. D.C. Speirs: "Encephalartos woodii: Resynthesis of female plants", Cycad Newsletter (US), Vol IV (1), Jan. 1981.
11. A.E. van Wyk & M.I. Claassen: "Sex reversal in Encephalartos umbeluziensis", Veld & Flora, December 1981.