Free The Tree by Colin Tudge Page A

naturalists felt, biology should have its “laws” too. This general feeling reinforced the idea that the apparent orderliness of nature, which is reflected in general terms like “bird” and “insect,” did indeed have deep origins.
    John Ray was outstanding among the seventeenth-century naturalists who sought to broaden the scope of classification, to include many more creatures than the herbalists had, and to devise ground rules for finding the true order of nature that lies behind appearances. Notably, in our present context, he distinguished two great categories of flowering plants—a distinction that still persists. Some flowering plants, he pointed out, have long, narrow leaves, like lilies and grasses; others have broad leaves. More than a century later the French taxonomist Antoine-Laurent de Jussieu pinned down the deep difference that lies behind this distinction. The embryos of all flowering plants, still within their seeds, have leaves, known as “cotyledons.” The embryos of narrow-leaved flowering plants, such as lilies, grasses, and palm trees, have only one cotyledon. The embryos of broad-leaved plants, like oak trees and daisies, have two cotyledons. Hence the two great groups of flowering plants: monocots and dicots (much more of this in Chapter 6). Jussieu’s discovery illustrates another great principle, in line with Aristotle’s musing over the number of legs: that the characters that really count, and really show who is related to whom, are often ones that are
not
particularly obvious; indeed, they are “cryptic.”
    Jussieu was a child of the Enlightenment, in which thinkers of all kinds sought to integrate all the wisdom of the world into one grand “rational” framework. The Enlightenment was centered in France, and Jussieu was only one of a host of late-eighteenth-century French biologists who made an enormous and lasting impact. Best known of them all was Jean-Baptiste Lamarck, who was a fine botanist and devised keys to aid identification. But the Enlightenment touched all of Europe, and perhaps the most influential Enlightenment biologist of all was a Swede, Carolus Linnaeus or Linneus (whose name is sometimes Germanized for no good reason to Carl von Linné). Linnaeus was primarily a botanist and led several expeditions deep into Europe, much of which in his day was still very wild and woolly, discovering many hundreds of new species. He was also a marvelous extrovert and led botanical expeditions from his native Uppsala with the local band out in front and everyone dressed in a uniform of his own design. This demonstrates once more how much easier it is to be a botanist than a zoologist. Animals faced with such a mob would surely have packed themselves off to Russia.
    More to the point, between the 1730s and the 1750s Linnaeus built upon the ideas of his contemporaries and predecessors to create the system of classification that is with us still, and is called “Linnean.” In truth, since Linnean classification has been significantly modified over the years, it should surely these days be called “neo-Linnean.” But so far as I know, I am the only person to use the term “neo-Linnean” (and will continue to do so until it catches on).
    At the root of Linnaeus’s classification is the “binomial” system of naming living creatures. Each creature has two names, as in
Quercus robur
or
Homo sapiens.
The first name is “generic,” denoting the name of the genus, and the second is the species. In truth, Linneus did not invent the binomial system from scratch—it is evident in the work of the medieval herbalists—but he made it formal. It remains one of the few items of language that is universally acknowledged worldwide. Absolutely unbreakable convention rules that these scientific names are always written in italic; that the generic name always begins with a capital letter; and that the specific name is always written lowercase, even when it is based on the name of a