You might want to know about this tropical aphrodisiac that really works, but I did not waste my time at a superb seminar asking details of it. Later, perhaps. But I can tell you it comes from Surinam, it is made from a liana as curare is, and this fellow from Harvard says that unlike rhinoceros horn and all that other stuff this one works. It is for males, by the way, and it is just one more example of the potentially (heh-heh) priceless plant products being threatened as the tropical forests of the world are raped.

During the time we sat in the National Geographic Auditorium to hear about plant conservation -- and remember the dull term really means cancer cures, economic windfalls in the tens of billions of dollars, and that aphrodisiac thrown in for good measure -- within that brief time yesterday a stretch of land as large as the Washington metropolitan area was leveled in tropical forests. They are vanishing at the rate of 54 acres a minute.

Peter Raven, director of the Missouri Botanical Garden, led off with a long talk packed with roughly 2 billion facts, most of them horrible, on the seriousness of plant loss in the world.

There are 250,000 species of plants in the world and on them life rests. It might be thought that if a tenth of these species become extinct (the current cautious estimate) it will be too bad, but then dinosaurs are extinct, too, and we still manage to get along.

Apart from the fact that the world would be much nicer if we still had dinosaurs, there is the other fact that without plants we cannot live, and the loss of 10 percent can be so severe that it's probably just as well we don't realize what we are losing -- in the sense that if we are going to die next week, it's just as well not to know about it.

He and other speakers gently, if cruelly, reminded us of a few facts perfectly well known but which we like to forget:

*Curare, now found in every hospital in the world, I suppose, and widely used in abdominal surgery and for other medical purposes, is still collected from tropical forests. We like to think that once we have the plant and analyze its chemical structure we can then duplicate it in a laboratory. This is by no means so true as we like to think. Curare has not been synthesized. It is still a plant product and without the plants we have no curare.

*The rosy periwinkle that comes from off the coast of Africa has utterly transformed the hazard of leukemia in children. Only a few years ago, if a kid got this cancerous disease his chance of life was hardly worth speaking of. With drug from the periwinkle he has an almost 95 percent chance of remission.

*Several years ago a kind of perennial corn was discovered in a small patch of a mountain farm in tropical America. There was not much of it and it would certainly have become extinct very soon, but its unusual qualities were noted (University of Mexico and University of Wisconsin scientists deserve credit). Among other interesting things, it affords resistance to seven diseases common to corn in the Midwest. It also grows in cooler, damper climates than now support the growth of corn. Its immediate potential is to save the world $3 billion a year. And yet it was almost lost, and tropical biologists have no doubt whatever that great numbers of plants equally valuable have been lost, and more will be.

*Everybody knows digitalis, the heart stimulant, comes from the foxglove plant. What is not so widely known is that some strains of the plant are heroically more useful in medicine than others. In other words, when you find a valuable plant and are grateful to have it, you may have something far more valuable than you realized, even though you appreciated its usefulness to begin with.

*There are plants, all tropical still, that produce liquid wax, an extraordinary thing in plants, from which gasoline can be manufactured. There are plants that offer an alternative to rubber, valuable because artificial rubber lacks some of the most important qualities of natural rubber from plants. And so on endlessly. How many priceless cures and how many economic treasures we are losing today can only be estimated, but the estimates of loss run not only in human comfort or cure, but in the megabillions of dollars.

Apart from the super-plants, the joyful things like rosy periwinkle, the tropical forests contain the bulk of the world's animals and birds and bugs, which face a common threat with the forests. There are more kinds of birds in one park in Peru than in all eastern North America. Many will become extinct, as everyone is tired of hearing, no doubt, before they are even properly identified, classified and studied.

Yesterday's day-long seminar was arranged and sponsored by the Garden Club of America (Marjorie Arundel was among the workhorses present and received an Award of Honor from World Wildlife Fund for her years of effort) and World Wildlife.

A few years ago, to turn to a peculiarly grim aspect of forest destruction, the population of the developed countries (us, the Russians, the Europeans) accounted for a third of the world's population. Today we are only a fourth, and within a few years we shall be only a sixth of that population.

And if you look at the proportion of the population under 15 years of age, you find it remarkably high in Third World tropical countries. They have their childbearing years ahead of them, so the imbalance between the rich developed countries and the extremely poor tropical countries will become greater as time passes.

Raven pointed out that Nicaragua has only 3 million people. The amount of American wealth already spent there suggests that dealings with the billions of a tropical populace may be costly, as population and poverty bring unholy pressures in the tropical world.

In spite of all that has been documented in recent years, there are still those, who seem to me virtually insane, who think modern technology will salve all wounds in the immediate future, and who even think "thinning the woods" and even greater reliance on expanding family farms and expanding families are a means of tropical self-sufficiency.

Dr. Thomas E. Lovejoy, the famous tropical biologist and tireless publicist of tropical conservation, said conservation cannot work unless there is economic development in the tropics. Otherwise, the pressures will become too great to preserve even the pitifully inadequate conservation parks in existence there. He cited a great iron ore deposit in the tropics, in which (for there are miracles still) the owners have cleared only 1 percent of their land, and have asked expert scientific help in using the other 99 percent in ways to avoid ruining the complex forest life.

If this sort of planning and enlightenment could prevail, it would be worth more than all the aphrodisiacs in Surinam.