The cedar apple rust fungus induces galls which in the spring produce wormlike
growths. Spores infect young apple trees, causing lesions on fruits and leaves.
The lingering death of a tree in my backyard has me thinking. The Eastern red cedar looked bad—shaggy, wasted, a dandruff of gray decline mixed in with the healthier bluish-green needles. We had seen the cause already, in the form of 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 small 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, from books and such, as cedar-apple rust, a parasite with a provocative life cycle that requires it to jump between juniper and apple hosts. (The Eastern red cedar, despite its name, is actually a juniper.) On the leaves and fruit of apple trees, this parasite manifests itself as leathery spots of discoloration. On junipers it appears as these woody galls. The apple and juniper forms of the parasite are different stages of a single life cycle that 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 gall, acting on instructions from the fungus, like an animal whose rogue cells produce a tumorous mass.
Rain revealed more. It rained for two or three days—a steady, soaking rain that had my sons whooping barefoot on the lawn. They were all excitement. “The parasite opened up!” they told me. Indeed. All over the 50-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 take a closer look. My oldest son poked at one and proclaimed it slimy. I tried its texture myself: wet gummy worms. Our gentlest touches marred them. I almost expected them to recoil.
We usually think of fungus as an unhealthy thing, a sign of disease. That is 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, symbionts, a fungus paired with an alga or a similar life form. 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 cut dead wood. When my sons climb to prospect for higher views, half their footholds are ledges of lichen or simple fungus.
I call 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 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 an individual, then the largest life forms we know are fungal, stretching for miles within the soil, their total mass rivaling that of the largest animals on earth—blue whales.
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 symbiont; 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 and water the plant needs; the plant in turn 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 percent of plants cohabit in such a manner, and some estimates go as high as 95 percent. 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 will find an arc of mushrooms in my front yard. It is this distribution that reveals hidden relationships, for the focus of the arc is an oak tree. The mushrooms are the genitals of fungi intimate with the tree. It is possible to trace thicker roots, barely concealed in the dirt, to aggregations of mushrooms.
