There is a painting by Asher Brown Durand called “Kindred Spirits,” which is often reproduced in books when the subject turns to the American landscape in the nineteenth century. Painted in 1849, it shows two men standing on a rock ledge in the Catskills in one of those sublime lost world settings that look as if they would take an expedition to reach, though the two figures in the painting are dressed, incongruously, as if for the office, in long coats and plump cravats. Below them, in a shadowy chasm, a stream dashes through a jumble of boulders. Beyond, glimpsed through a canopy of leaves, is a long view of gorgeously forbidding blue mountains. To right and left, jostling into frame, are disorderly ranks of trees, which immediately vanish into consuming darkness.

I can’t tell you how much I would like to step into that view. The scene is so manifestly untamed, so full of an impenetrable beyond, as to present a clearly foolhardy temptation. You would die out there for sure-shredded by a cougar or thudded with a tomahawk or just left to wander to a stumbling, confounded death. You can see that at a glance. But never mind. Already you are studying the foreground for a way down to the stream over the steep rocks and wondering if that notch ahead will get you through to the neighboring valley. Farewell, my friends. Destiny calls. Don’t wait supper.

Nothing like that view exists now, of course. Perhaps it never did. Who knows how much license these romantic johnnies took with their stabbing paintbrushes? Who, after all, is going to struggle with an easel and campstool and box of paints to some difficult overlook, on a hot July afternoon, in a wilderness filled with danger, and not paint something exquisite and grand?

But even if the preindustrialized Appalachians were only half as wild and dramatic as in the paintings of Durand and others like him, they must have been something to behold. It is hard to imagine now how little known, how full of possibility, the world beyond the eastern seaboard once was. When Thomas Jefferson sent Lewis and Clark into the wilderness, he confidently expected them to find woolly mammoths and mastodons. Had dinosaurs been known, he would almost certainly have asked them to bring him home a triceratops.

The first people to venture deep into the woods from the East (the Indians, of course, had got there perhaps as much as 20,000 years before them) weren’t looking for prehistoric creatures or passages to the West or new lands to settle. They were looking for plants. America’s botanical possibilities excited Europeans inordinately, and there was both glory and money to be made out in the woods. The eastern woods teemed with flora unknown to the Old World, and there was a huge eagerness, from scientists and amateur enthusiasts alike, to get a piece of it. Imagine if tomorrow a spaceship found a jungle growing beneath the gassy clouds of Venus. Think what Bill Gates, say, would pay for some tendriled, purply lobed piece of Venusian exotica to put in a pot in his greenhouse. That was the rhododendron in the eighteenth century-and the camellia, the hydrangea, the wild cherry, the rudbeckia, the azalea, the aster, the ostrich fern, the catalpa, the spice bush, the Venus flytrap, the Virginia creeper, the euphorbia. These and hundreds more were collected in the American woods, shipped across the ocean to England and France and Russia, and received with greedy keenness and trembling fingers.

It started with John Bartram (actually, it started with tobacco, but in a scientific sense it started with John Bartram), a Pennsylvania Quaker, born in 1699, who grew interested in botany after reading a book on the subject and began sending seeds and cuttings to a fellow Quaker in London. Encouraged to seek out more, he embarked on increasingly ambitious journeys into the wilderness, sometimes traveling over a thousand miles through the rugged mountains. Though he was entirely self-taught, never learned Latin, and had scant understanding of Linnaean classifications, he was a prize plant collector, with an uncanny knack for finding and recognizing unknown species. Of the 800 plants discovered in America in the colonial period, Bartram was responsible for about a quarter. His son William found many more.

Before the century was out, the eastern woods were fairly crawling with botanists-Peter Kalm, Lars Yungstroem, Constantine Samuel Rafinesque-Schmaltz, John Fraser, André Michaux, Thomas Nuttall, John Lyon, and others pretty much beyond counting. There were so many people out there, hunting so competetively, that it is often not possible to say with any precision who discovered what. Depending on which source you consult, Fraser found either 44 new plants or 215, or something in between. One of his uncontested discoveries was the fragrant southern balsam, the Fraser fir, so characteristic of the high ranges of North Carolina and Tennessee, but it bears his name only because he scrambled to the top of Clingmans Dome just ahead of his keen rival Michaux.

These people covered astonishing sweeps, for considerable periods. One of the younger Bartram’s expeditions lasted over five years and plunged him so deeply into the woods that he was long given up for lost; when he emerged, he discovered that America had been at war with Britain for a year and he had lost his patrons. Michaux’s voyages took him from Florida to Hudson’s Bay; the heroic Nuttall ventured as far as the shores of Lake Superior, going much of the way on foot for want of funds.

They often collected in prodigious, not to say rapacious, quantities. Lyon pulled 3,600 Magnolia macrophylla saplings from a single hillside, and thousands of plants more, including a pretty red thing that left him in a fevered delirium and covered “almost in one continued blister all over” his body; he had found, it turned out, poison sumac. In 1765, John Bartram discovered a particularly lovely camellia, Franklinia altamaha; already rare, it was hunted to extinction in just twenty-five years. Today it survives only in cultivation-thanks entirely to Bartram. Rafinesque-Schmaltz, meanwhile, spent seven years wandering through the Appalachians, didn’t discover much, but brought in 50,000 seeds and cuttings.

How they managed it is a wonder. Every plant had to be recorded and identified, its seeds collected or a cutting taken; if the latter, it had to be potted up in stiff paper or sailcloth, kept watered and tended, and somehow transported through a trackless wilderness to civilization. The privations and perils were constant and exhausting. Bears, snakes, and panthers abounded. Michaux’s son was severely mauled on one expedition when a bear charged him from the trees. (Black bears seem to have been notably more ferocious in former times; nearly every journal has accounts of sudden, unprovoked attacks. It seems altogether likely that eastern bears have become more retiring because they have learned to associate humans with guns.) Indians, too, were commonly hostile-though just as often bemused at finding European gentlemen carefully collecting and taking away plants that grew in natural abundance-and then there were all the diseases of the woods, like malaria and yellow fever. “I can’t find one [friend] that will bear the fatigue to accompany me in my peregrinations,” John Bartram complained wearily in a letter to his English patron. Hardly surprising.

But evidently it was worth it. A single, particularly valued seed could fetch up to five guineas. On one trip, John Lyon cleared £900 after expenses, a considerable fortune, then returned the next year and made nearly as much again. Fraser made one long trip under the sponsorship of Catherine the Great of Russia and emerged from the wilderness only to find that there was a new czar who had no interest in plants, thought he was mad, and refused to honor his contract. So Fraser took everything to chelsea, where he had a little nursery, and made a good living selling azaleas, rhododendrons, and magnolias to the English gentry.