Rust, Part 1 of 2

The Stoics asserted that human beings sprang forth from the soil of hill and plain like sprouting mushrooms.
Francesco Redi

Our move brought me over a lift-bridge in the middle of a rainy night. Tracy had taken the place and set up housekeeping, and now she was showing me the way home. Our sons were in the back, one talking, the other sleeping. The road curved into the moist dark. "I'll bet you're wondering what I got you into," Tracy said.
But in the morning the place was sunshine and the chatter of finches. We were to live in a village in the upper Midwest. The front of our place was a busy and badly paved road; the back was a straggling wood. Winter nights, you'd be able to see all the way through the naked forest to the houses on the other side. But for now it was spring and I had the illusion of a wilderness.
The Eastern red cedar tree in our back yard looked bad—shaggy, wasted, a dandruff of gray decline mixed in with the healthier bluish-green needles. We saw the cause: little spiky galls hanging here and there like drab Christmas ornaments. Each of these ornaments was smaller than a golf ball and seemingly made of wood, which might make you think it was some healthy part of the tree. I picked one off. Each little spike was a spout: a hole surrounded by a sharp woody projection. The ball resisted pressure only as much as a fruit might. Carrying it to the cement walk, I crushed it under my heel. It wasn't difficult. Inside, the thing was pulpy and fibrous, its strands of vegetable matter radiating from a tight core. Its wet texture was like that of the new wood you can find under a tree's bark.
I knew this as cedar apple rust, a parasite with a provocative life cycle. On the leaves and fruit of apple trees, this fungus manifests itself as leathery patches of discoloration. On red cedar trees, it takes the form of these woody galls. The apple and cedar forms of this parasite are different stages of a single life cycle which involves both sexual and asexual spores.
To look at it, though, I wouldn't have recognized this sphere as alien to the tree, made as it was of the tree's own tissues. The tree itself makes the sphere, acting on instructions from the fungus, like an animal body producing a tumorous mass at the command of rogue cells. My sons gathered a few and smashed them with a tenderizing mallet to examine their insides.
Rain revealed more. It rained for two or three days, a steady soak that had my sons whooping barefoot on the lawn. One day they were all excitement: "The parasite opened up!"

             . . . a sea-change
Into something rich and strange. 

Indeed. All over the fifty-foot tree, the galls had effloresced. Through each spiky spout, a vivid orange tentacle projected. It seemed as if the tree had collided with a swarm of sea anemones.
I bent a bough down so the boys could see. My older son poked at one gall and proclaimed it slimy. I tried its texture myself: wet gummy worms. Our gentlest touches marred them. I almost expected them to recoil.

*
It used to be said that a fungus was a sort of defective or degenerate plant, one that lacked chlorophyll and so could not make its own food. It was thus reduced to feeding off the work of others—grubbing in the soil to devour dead animals, fallen leaves, and damp wood.
Biologists know better now, partly because of advances in genetics. In the last few years, DNA sequencing has revealed strong evidence for all sorts of things we hardly could have suspected—that whales belong among the even-toed hoofed mammals, that dinosaurs and birds are more closely related to crocodiles than turtles are. The method behind this is to look for similar strings of DNA, then analyze them statistically. All life on earth comes from a common stock; the more dissimilar two life forms are genetically, the longer it's been since they diverged. By applying sophisticated mathematical models, geneticists can estimate how long it takes for certain kinds of differences to arise. By comparing these numbers, they can deduce how closely related different kinds of living things are.
But this re-evaluation of relationships goes deeper than the shifting of animals among orders. Our vision of life at the most basic levels has altered too; the kingdoms, the very fundaments of Linnaean biology, have had to be shifted about. The fungi comprise their own kingdom now. We understand, better than we did at least, what they are. Certain organisms we had called fungi because they were slimy and repulsive and because we didn't know where else to put them—the slime molds, for example—have been exiled from the kingdom. That is not too hard to take, because few of us encounter slime molds with any regularity.
What's harder to take is that fungi turn out to be our kinsmen. They are not plants at all; they are closest to the animals—to us.
*
We usually think of fungus as an unhealthy thing, a sign of disease. That's a slander, for parasitism is only one of the possibilities of fungi.
In the woods behind my house I find uncountable lichens. These are, as every high school student learns, symbiotes, a fungus paired with an alga or a similar lifeform. They are the surface I touch when I lay my hand on a fallen tree; they are the first flaky layer my handsaw bites through when I gather dead wood. When my sons climb to prospect for higher views, half their footholds are ledges of lichen or simple fungus.
I called them uncountable. This is only partly because they are numerous. The other reason I can't quantify them is that they lack integrity. The whole leeward side of a certain box elder tree is crusted with green: where does one lichen end and another begin?
Fungi are often colonial, rather than singular. A million fungal filaments in a patch of soil may be in communication of a sort, all of them sending strands toward a food source when one detects it. There is, of course, no brain, no central command, merely a shared purpose. If we consider one such aggregation a single individual, then the largest life forms we know are fungal: stretching for miles within the soil, their mass rivaling that of the blue whales or perhaps even the redwoods.
If the individuality we tend to think of as fundamental is lacking in the fungi, then so are the species boundaries. Lichens are only one kind of symbiosis; the fungi have many. One style, for example, is the mycorrhiza, a combination of fungi with the roots of a plant. The fungi reach where the plant cannot, bringing in minerals the plant needs; the plant shares the food it makes from light and water. Though most people are perhaps not familiar with this arrangement, it is the basis of life as we know it. At least 80% of plants cohabit in such a manner—some estimates go as high as 90. The boundaries are not exactly where we are accustomed to draw them, because, practically speaking, the average tree or weed or grass is not merely a plant, but a combination of plant and fungus.
It is not easy to grasp this, or to see it without benefit of excavation, dissection, and microscopy. But the signs are visible, if you look. Sometimes in wet weather I find an arc of mushrooms in my front yard. It is this arcing distribution that reveals hidden relationships, for the focus of the arc is a maple tree. The mushrooms are the genitals of fungi intimate with the tree. It is possible to trace its thicker roots, barely concealed in the dirt, to aggregations of mushrooms.
To be continued.

This story originally appeared in Discover.