The Tree Read Free Page B

light (although, like the trees of cacao and tea and coffee, the banana prefers a little shade).
    In fact, there are many lineages of trees—quite separate evolutionary lines that have nothing to do with one another except that they are all plants. Many plants, in many of those lineages, have independently essayed the form of the tree. Each achieves treedom in its own way. “Tree” is not a distinct category, like “dog” or “horse.” It is just a way of being a plant. The different kinds have much in common, and it is good and necessary to have some feel for what is essential. But the essences of nature will not be pinned down easily. In the end,
all
definitions of nature are simply for convenience, helping us focus on the particular aspect that we happen to be thinking about at the time. There is no phenomenon in all of nature—whether it’s as simple as “leg” or “stomach” or “leaf” or more obviously conceptual like “gene” or “species”—that does not take a variety of forms, and that cannot be looked at from an infinite number of angles; and each angle gives rise to its own definition. A horse cannot be encapsulated, as Charles Dickens’s Thomas Gradgrind insisted in
Hard Times,
as “a graminivorous quadruped.” There is more to horses than that. The way we define natural things influences the way we treat them—whether we speak of wildflowers or of weeds, of Mrs. Tittlemouse or of vermin. But in the end nature is as nature is, and we must just try with different degrees of feebleness, and for our own purposes, to make what sense of it we can.
    For the purposes of this book, the child’s definition of “tree” will serve—albeit with slight elaboration: “A tree is a big plant with a stick up the middle—or could be, if it grew in the right circumstances; or is very closely related to other plants that are big and have a stick up the middle; or resembles a big plant with a stick up the middle.” It is clumsy, but it will have to do. So to the next childish question.
    WHY BE A TREE?
    A nonliving thing is passive. The atoms of which a stone is composed sit there for as long as it endures—until it is melted in some volcano, or dissolved by acid rain. But living things are restless, through and through. As soon as some living cell has constructed some protein, as part of its own fabric, it starts to dismantle it again. This constant self-renewal, powered by an endless intake of energy, is called metabolism.
    Metabolism—the basic business of staying alive—is half of what living things do. The other half is reproduction. It is not vital to reproduce in order to stay alive. Indeed, reproduction involves sacrifice; reproduction, as we will see later in this book, is often the last fling: many a tree dies after one bout of it. But it is essential nonetheless. At least, all creatures that do not reproduce die out. However successfully an organism may metabolize, sooner or later time and chance will finish it off. Everything dies. Only those that reproduce endure—or, at least, their offspring do. All individuals are part of lineages, offspring after offspring after offspring.
    But then, too, each creature finds itself in the company of other creatures, of its own kind and of different kinds. To some extent they are its rivals, to some extent it needs them—for food, shelter, mates, or whatever. Each successful creature, then—each one that survives at all, that is—must come to terms with the others around it.
    All of life’s requirements—metabolism, reproduction, and the business of getting along with others—are difficult. Each creature must solve life’s problems in its own way. There is no perfect, universal life strategy. Each has its own advantages and drawbacks.
    So it can pay a creature to be very small; or it can pay to be big. Each mode has its pros and cons. A plant that is big like a tree can stretch farther up into the sky, and so capture more of the sun’s energy;