The Forest Unseen: A Year's Watch in Nature (8 page)

Böhme’s ideas did not become widely known until botanical physicians learned of his work. His doctrine helped their trade by providing a theological cabinet in which to store their herbal remedies. Many physicians already used the external forms of plants as mnemonics with which to remember their medicinal functions: the scarlet juice of bloodroot for disorders of the blood, toothwort’s indented leaves and white petals for toothache, coiled roots of snakeroot for snakebite, and dozens more. Now, the healers had a theory with which to organize and justify their practices. The shape, color, and growth of plants indicated their divine healing purpose. The showy, scented blossoms of the apple tree were intended to heal disorders of fertility and complexion; red, peppery plants were stamped with the sign of blood and anger, and so could be used to stimulate the circulation or the spirit. The
Hepatica
’s three-lobed purple leaves bore the liver’s mark.

The use of external marks to deduce and remember the medicinal function of chemicals inside plants became known as the Doctrine of Signatures. The idea spread across Europe and attracted the attention of the scientific elite. They tried to haul the herbalists’ doctrine out of folklore and into the then modern science of astrology. The signature in each plant, they claimed, reflected God’s purpose, but it did so through the complex cosmology of the planets, moon, and sun. The
apple blossom was governed by Venus, hence its beauty and its healing powers. Jupiter governed all hepatic plants, and Mars ruled the warlike peppers. Correct diagnosis and treatment therefore required that a qualified scientist cast a horoscope and create a remedy incorporating his extensive, expensive knowledge of the celestial spheres and their influence on both plants and the human body. The scientific establishment railed against the country quackery of the simpleminded botanists while expropriating the quacks’ remedies for use in an updated astrological medicine.

This tension between the medical establishment and the quacks continues, of course. The astrological Doctrine of Signatures now finds itself out of favor. Our physicians no longer believe that God left providential medicinal hints in the shapes of leaves and in the arrangement of the stars. We should not, however, be too quick to dismiss the Doctrine of Signatures as a trifling superstition. As a method of cultural transmission of medical knowledge, the doctrine was a powerful organizing device, richer and perhaps more coherent than the mnemonics used by modern physicians to navigate their large stores of knowledge. The method gave healers, most of whom could not read, linguistic cues to connect patients’ symptoms with the sometimes arcane details of botanical identification and medical knowledge. The Doctrine of Signatures persisted for so many years not because our ancestors were simpleminded but because it was so useful.

Hepatica
’s name reveals our culture’s propensity for naming plants after their uses. This method of naming helps us to remember humanity’s dependence on plants for medicines and foods. But utilitarian names can also stand in the way of a full experience of nature. For example, our nomenclature has its teleology wrong.
Hepatica
exists not to serve us but to live out its own story, one that began in the forests of Europe and North America millions of years before humans came to be. Likewise, our naming imposes tidy categories on nature. These may
not reflect life’s complicated genealogies and reproductive exchanges. Modern genetics suggests that boundaries in nature are often more permeable than we suppose when we name “separate” species.

On this bright morning in early spring, the
Hepatica
’s confident welcome of the first warm sun and flying bees reminds me that the mandala exists independent of human doctrines. Like all people, I am culture-bound, so I only partly see the flower; the rest of my field of vision is occupied by centuries of human words.

T
he mandala is a molluskan Serengeti. Herds of coiled grazers move across the open savanna of lichens and mosses. The largest snails travel alone, plying the crazy angled surfaces of the leaf litter, leaving the mossy hillsides for the nimble youngsters. I lie down on my belly and creep up on a large snail that sits at the edge of the mandala. I lift the hand lens to my eye and shuffle closer.

Through the lens, the snail’s head fills my field of vision—a magnificent sculpture of black glass. Patches of silver decorate the shining skin, and small grooves run across and down the animal’s back. My movements cause mild alarm; the snail withdraws its tentacles and hunches back into the shell. I hold my breath and the snail relaxes. Two small whiskers poke their way out of the chin, waving in the air before reaching down and touching the rock. These rubbery feelers move like fingers reading Braille, touching lightly, skimming meaning from the sandstone script. Several minutes later a second pair of tentacles launches out from the crown of the snail’s head. They reach upward, each with a milky eye at its tip, and wave at the tree canopy above. My own eye bulges at the snail through the lens, but this monstrous globe seems to be of little concern to the snail, which extends its eyestalks farther. These fleshy flagpoles now reach wider than the shell and swing wildly from side to side.

Unlike its relatives the octopi and squid, this land snail has no sophisticated lens and pinhole through which to form crisp images.
But just how fuzzy the world appears to a snail is a mystery. Scientists have difficulty asking the snails what they perceive, and this communication problem slows the leading edge of snail vision research. The only experimental success in this area has come from borrowing the tricks of circus trainers and teaching snails to eat or move when they see a signal. So far, these performing gastropods have shown that they can detect small black dots on a white test card. They can also distinguish between gray and checkered cards. As far as I know, no one has yet asked a land snail whether it can see color, motion, or a flaming hoop.

These experiments are fascinating, but they leave aside a larger question: what is a snail “seeing”? Do snails see as we do, with images of checkered cards appearing in their gastropod minds? Do they experience private displays of light and dark, processed by tangles of nerves into decisions, preferences, and meaning? The human body and the snail body are made from the same wet pieces of carbon and clay, so if consciousness grows out of this neurological soil, on what grounds do we deny the snail its mental images? No doubt what it sees is radically different, an avant-garde movie of strange camera angles and lurching forms, but if the human cinema is caused by nerves, we have to allow for the startling possibility that the snails have a similar experience. But our culture’s preferred story is that the snail movie plays to an empty house. Indeed, the theater has no screen. The snail has no internal subjective experience, we claim. Light from the eye’s projector merely stimulates the snail’s ductwork and wiring, causing the hollow theater to move, eat, mate, and keep up the appearance of life.

The snail’s head explodes, ending my speculations. The black dome is split by a knot of cloudy flesh. The knot pushes out, forward, then the snail turns to face me. The tentacles form an X, radiating away from the bubbling, doughy protrusion at the center. Two glassy lips push out, defining a vertical slit, and the whole apparatus heaves downward, pressing the lips to the ground. I watch, saucer-eyed, as the snail starts to glide over the rock, levitating across a sea of lichen. Tiny beating
hairs and ripples of infinitesimally small muscles propel the ebony grazer on its path.

From my prone position I see the snail pause amid lichen flakes and black fungus spiking from the surface of oak leaves. I peek over the lens and suddenly it is all gone. The change of scale is a wrench into a different world; the fungus is invisible, the snail is a valueless detail in a world dominated by bigger things. I return to the lens world and rediscover the vivid tentacles, the snail’s black-and-silver grace. The hand lens helps me harvest the world’s beauty, throwing my eyes wide open. Layers of delight are hidden by the limitations of everyday human vision.

My snail vigil ends when the sun breaks out from behind a cloud. The morning’s soft humidity has lifted, and the snail heads toward El Capitan, or a smallish rock, depending on how you see the world. Here the snail touches a tentacle to the rock, then turns its entire head upside down and stretches up. The neck and head rubber-band into a giraffe’s, farther, a little farther, then the chin hits the rock, spreads itself into a pad, and the whole snail lifts up from the ground in a no-handed chin-up. Gravity blinks and the animal flows impossibly upward and continues its journey, upside down, into the rock crevice. I look up, out of the lens world, and the Serengeti has emptied. The grazers have evaporated in the sun.

M
y walk to the mandala has become fraught. Every footstep threatens to squash half a dozen wildflowers, and so I step slowly, trying to pick out a way that does not leave a trail of crushed beauty. The mountainside is heavily peppered with green and white; half the leaf litter’s surface is covered by newly grown leaves and flowers.

It is hard, though, to concentrate on my feet when the year’s first butterflies and migratory warblers are flying above me. An eastern comma, a rufous butterfly named for the white curl on its hindwing, flicks past my head and lands on a hickory trunk. The warm sun has roused it from its winter hibernation, hidden under a bark flake. A black-throated green warbler and a black-and-white warbler, both recently returned from Central America, sing from the bluff. The forest’s renewed life seems to crowd in on me from all sides, lifting my spirits with its unrestrained vigor.

At the mandala I find a starburst of white flowers, a hundred blossoms shining out at the world. Spring beauty flowers with pink-streaked white petals grow low to the ground, intermixed with purple
Hepatica
. A few rue anemones emerge from the mandala’s edge, their nodding white flowers held finger-length above the leaf litter. Toothwort reaches tallest, just above ankle height, holding flowers with long white petals in clusters at the tips of sturdy stalks. Each flower trails a comet’s tail of lush green growth, erupting life from the mat of dead
leaves. The contrast with the wintry trees above the mandala is dramatic. Tree buds are barely broken open.

Spring wildflowers take advantage of the trees’ sluggishness, rushing through their reproduction and growth before the tree canopy steals life-giving photons. Although the March sun is still low, its rays are strong enough to burn the back of my neck as I sit. We have reached the peak of the year’s cycle of light intensity below the canopy. Winter’s hold is broken with blazing force, unlocking constellations of flowers and a cascade of animal life.

The plants that festoon the mandala are collectively called spring ephemerals. This name captures their meteoric brilliance in springtime and their rapid fade in the summer sun, but the name belies their secret underground longevity. These plants grow from subterranean storehouses, some of them growing from hidden belowground stems called rhizomes, others emerging from bulbs or tubers. Every year, the plants send up leaves and flowers, then return to covert quiescence. The flowers’ push into the cool spring air is therefore fueled by food stored up from the previous year. Only after the plants have leafed out does photosynthesis boost their balance sheet. This strategy helps them persist in the choked, light-hungry world of the mandala. Some of these stems may be hundreds of years old, having slowly crept across the forest floor by growing a few centimeters of horizontal stem each year. These plants survive on the food gained during a few short weeks of springtime sun.

Once the ephemerals have unfurled their leaves, they reap sunlight and carbon dioxide at a furious rate. The breathing holes in their leaves, the stomata, are thrown wide open. Leaves are stuffed with enzymes ready to concoct nutritious molecules out of air. These plants are the fast-food junkies of the forest: they eat rapidly, rushing to get through the meal before the trees block out the light. The ephemerals require bright sunlight to sustain this gluttony. Their hyped-up bodies cannot tolerate shade.

Other plants in the mandala take a slower road. The toadshade trillium
pokes up a trio of dappled leaves between the
Hepatica
and spring beauty plants, but it is not seeking a quick spurt of growth. Toadshade trillium’s leaves have few enzymes with which to harness sunlight, so they cannot match the ephemerals’ growth rate. Their thrift is rewarded when the tree canopy closes; low levels of enzymes are cheap to maintain, so the trillium can make a sugary profit in the deep shade of summer. We are at the starting line for the annual botanical race for the mandala’s limited space. Evolution has produced a wonderful diversity of running styles: Carolina spring beauty is a muscled-up sprinter, trillium is a lean distance runner.

The bright burning lives of the ephemerals ignite the rest of the forest. Their growing roots reinvigorate the dark life of the soil, absorbing and holding the nutrients that would otherwise be flushed out of the forest by the spring rains. Each root secretes a nutritious gel, creating a sheath of life around its hairy tip. Bacteria, fungi, and protists are a hundred times more abundant in this narrow halo, and these single-celled creatures provide food for nematodes, mites, and microscopic insects. The grazers are preyed upon by even larger soil-dwellers such as the bright orange centipede that shimmers back and forth over the mandala as I sit watching. The centipede is longer than my hand is wide, so big that I can see each segment on its legs as the body undulates between the sources of its life, the flowers.

A few days ago my contemplation of the flowers was broken by a fiercer predator than this centipede. A palm-sized ball of gray fur shot out of the ground, then dove back into another hole, accelerating like a dustball pulled into a vacuum cleaner. A few minutes later I heard rustling and high-pitched squeaks from the other side of the mandala. I saw just enough of the sooty fur and stubby tail to know that the terror of the leaf litter was prowling the mandala: a short-tailed shrew.