Raising crocodiles for fun and profit is not, actually, the sort of project you expect the National Academy of Sciences to foster, but they do, as you may read for yourself in their booklet "Crocodiles as a Resource for the Tropics."

The same august academy also has a booklet, "Butterfly Farming in Papua New Guinea." The academy is a fertile field for information about guinea pigs as food animals for the tropics (you just raise them in cardboard boxes under the bed, and the beauty of it all is you eat your rack of guinea pig all at once and don't have to worry about leftovers in the icebox, rare in the tropics).

Behind these ventures is Noel Vietmeyer, who has as good a claim to the title of Most Valuable Man in the Capital as anybody else you are likely to see proposed. And greater claim than most, since he is intelligent, a superb communicator, serious, selfless, loyal, courteous, kind. And more.

In early middle age he has silver hair, a great blessing, since he will look the same for the next 40 years, and he has a boy-next-door smile he cannot conceal for more than a minute or two at a time, as if he somehow escaped the blows and burdens that ruin the good looks of most public benefactors.

His life is spent searching for plant and animal crops that could become priceless additions to the world's protein supply, with small excursions into such projects as the crocodiles and butterflies that are not especially good to eat, but which can add to the woeful supply of dollars in many Third World families.

But mainly it's food. He phoned me recently:

"You know we were talking last year about Andes stuff," he said, "and I've just got back with some fascinating things and thought you might want to try raising some anu and oka and ullucu. All delicious and all neglected."

These are not, thank God, fuzzy little barbecue items you raise under the bed, but tubers grown for centuries in the high mountains of Peru, Bolivia and Ecuador. Most of these rarities are lumpy, waxy and delicious as well as nourishing, according to Vietmeyer, and before you say it's nonsense to raise food tubers of the Andes in this nonmountainous capital, you should think of the potato.

That, too, is an Andean tuber, used to warm days, cold nights, pure air, and yet it flourishes in Ireland, where it never gets either hot or cold, and in Washington, where it's always either hot or cold but utterly un-Andean all the same.

When the Spanish, who settled the tropical countries south of us, looked around them they saw primitive people with deplorable diet and religion and promptly set themselves the task of improving both.

The Indians were taught to grow such godly crops as wheat and to give up such pagan crops as amaranth, which was used in religious ceremonies that need not be dwelt on here. And rich though South America is in marvelous food crops, the only ones we have taken seriously are corn and potatoes.

"But all the others are equally valuable, most likely," said Vietmeyer, squatting on the floor of his academy office with a small portable electric wok on which he was roasting amaranth seeds. "Have some."

Amaranth seeds are small as poppy seeds and when heated until 10 percent of them pop up off the hot iron they are delicious, between sesame seed and poppy seed in flavor.

The academy's Advisory Committee on Technology Innovation (the rather grand name for Vietmeyer's office) has scholarly tables showing the surprising food value of many of these long-ignored tropical crops that have all but disappeared in competition with civilized crops.

But you have only to think of corn and potatoes, utterly unknown to the "civilized" world until recent centuries, to comprehend how easily and quickly an unknown crop can become a mainstay of people everywhere.

"Of course there were Presbyterian ministers in Scotland," Vietmeyer said with a close eye on the amaranth seeds (you don't want them to burn, just toast lightly, like very moderate sinners in hell), "who said potatoes could not be wholesome food since the Bible says nothing at all about them. Besides, the leaves and flowers are poisonous and the tubers are ugly and lumpy and grow under the ground in darkness. Devil's food. Not fit for Christians."

Though the Irish, of course, soon started eating them. And, grimly, also starved when the crops failed in the last century, which brings Vietmeyer to another of his urgent points.

"The Indians had seven cultivated varieties of potato, plus 150 or so wild kinds, never tried by the Europeans. The genetic base of the Irish potato was extremely narrow, and when disease struck, it ruined everything, but there are other potatoes they knew nothing about that would have survived the ruinous blight."

All civilized people now know the importance of genetic diversity in crops. Curiously, the more learned and experienced a man is, the more likely he is to value weeds and wild things, while the ignorant and superficial man looks down his nose at anything he cannot find at Magruder's or Sears.

But while everybody now agrees on the prudence of a large genetic pool for all our big food crops, hardly anybody (except the Vietmeyers of the world who one hopes are increasing at a fair rate) seriously believes there is any problem now. After all, the potato blight is over and done with.

Vietmeyer reminds us of the corn crisis of the 1970s. This was a fascinating disaster. It had all the possibilities of toppling the world, yet not every American even knows it occurred. I didn't, for one.

The southern leaf blight struck in a small way in the 1960s, then nothing much happened until it struck with such force that many farmers lost half their crop. Now the statistics of corn are complex and worth great study, but in a nutshell if American corn failed, the world as we know it would go to pieces.

Fortunately, new strains of corn were introduced with such lightning speed that hardly any disruption was felt. But if those strains had not been there, corn would have vanished as the potatoes did in Ireland in the 1840s.

The genetic base of today's corn is narrow. Only six strains are involved, of all the multitude of strains that could have been. To put it plain, corn is a miracle perfected over the centuries, but the genetic steps by which it achieved perfection have been tossed aside once they served their purpose. So you have a fragile miracle at the mercy of such inevitable natural disasters as mutating disease organisms, without thinking how you might need to reconstruct this miracle in an emergency. Genetically, as one scholar put it, the failure to care for wild progenitors is like taking stones from the foundation to repair the roof.

Extraordinary pre-corns, as you could call them, have been discovered. Sometimes in a patch so small that their whole genetic treasure could go down the hatch in one bowl of porridge. Surely few projects are so worthwhile as securing a wide genetic base for all our big crops. What if, when the corn blight hit, the corns we had on hand did not happen to have the genes to resist that blight? Clearly, the more corns and the more genes you have, the better. Such insurance policies for corn and many another crop must be sought, often in remote unpleasant places by scientists with the imagination and experience to perceive that elegant table corn varieties may yet depend on genes from virtual weeds in some Andean wilderness.

Vietmeyer, whose amaranth did not burn, after all, despite his divided attention to it, is not really a corn guy or a crocodile or butterfly guy. He is more a flying-bean guy -- wonderful crop of high protein that may yet prove to be a savior of the tropics, where the soybean cannot be made to flourish. And what about these tubers from the Andes -- for all you know future centuries may revere this fellow as Father of the Ullucu.

He started out in New Zealand (his great-grandfather, a Scotsman being trained at the Royal Botanic Gardens, London, on the spur of the moment decided to emigrate himself) with normal interests. He went to the university there, then to Berkeley for advanced degrees, intending to become a nice chemist and poison everybody, but he met a great man -- great in his effect -- who interested him in unusual crops. Things like plants that produce genuine rubber (the genetic base of rubber in Southeast Asia is shockingly narrow) and plants that produce oil equal to that of the sperm whale. Did you know, he says, that until quite recently all automobile transmissions used oil from the endangered sperm whale? That whale's meat is virtually inedible and useless; they have been slaughtered just for the oil. This plant may save them yet.

And there are priceless plants that are useless for agribusiness, but which may be worth more than gold for their proteins and amino acids when grown in tiny patches by the poor in the tropics.

The hours race by with Vietmeyer. O my God. The whole academy building is empty. It's supper time. The whole afternoon is gone. A year of afternoons would not be too many.

"Hey," you holler at him as you leave and he heads belatedly for his car, "how'd those seeds of Canna warscewiczii do that I sent you last year? You think their tubers have any promise as a food crop?"

"Wow, I don't know," he hollers back. "I gave them to a guy to grow and haven't heard. Me, I don't grow anything. Got a black thumb."