Law and Order in the Plant World

Today is the 302nd anniversary of Linnaeus's birth. His is a curious legacy - revered and derided - remembered and forgotten - contemporary and anachronistic. Most of today's botanists regard him as a towering fossil; we know his L. marks thousands of plant names as part of the Linnaean foundation on which all modern plant names are based. We also know that many modern botanists are annoyed by the linearity, order, and equivalence implied in this genus-species system we inherit. Evolution has not been so complicit with human attempts to pigeon-hole the whole of creation; as Harold Bold often said: "Nature mocks at human categories."

And it was categorization that Linnaeus was all about. Today's significant holdover from Linnaeus's work is his consolidation of the binomial system of nomenclature. Linnaeus systematically brought every available plant into compliance with his way of naming and categorizing. The simplicity and thoroughness with which Linnaeus applied his way of naming plants proved of immediate and international value, sweeping away the awkward and forgetable. Today, through international agreement, we base the Code of Botanical Nomenclature on his 1753 Species Plantarum.

But for Linnaeus's contemporaries, most of whom idolized him, the immediate value of his publications was the way he organized plants. Linnaeus created a straight-forward method of grouping plants, a system that was easily memorized and utilized. For the first time in plant studies, anyone could study a new plant and know where to file it away - that is, how to classify the plant.

As a young man, Linnaeus had fallen as a thrall of sex, or more accurately, he was among the first generation of botanists who came to study plants with the awareness that seed are the fallout of sexual reproduction. Only a few years before his birth had it been made clear that pollen is the male generative force, analagous to human sperm. Linnaeaus took that fresh concept and ran with it. It was obvious to him that reproduction was crucial to preservation of every species, and the salient characteristics of reproductive organs should be directly correlated with the definition or nature of each different species. The result was his sexual system of classifying plants. Plant genera (and therefore the included species) could be grouped into Classes based on numbers and character of stamens, and within the Classes, into Orders based on the numbers and characteristics of pistils or further information on stamens.

The popularity of the sexual system of classifying plants was short-lived however. Within just a few years of Linnaeus's death, botanists published systems that grouped genera into families that seemed more "natural" - families that reflected the natural affinities of different groups of plants - affinities that would be considered ancestral and evolutionary a century later. So we are left with the binomial system of nomenclature as the residual legacy of Linnaeus's work.

But not so fast. In celebration of Linnaeus's 300th birthday two years ago, I decided it would be fun to attempt organizing a few salons that replicated the experience people would have had with Linnaeus's methods. I pulled out his simple system, assembled groups of people, and worked with the students through many plant samples. What a revelation. Of course there was no way we discovered that Linnaeus's sexual system has anything to say about how plants should be grouped or classified. What we did learn was how quickly his system cut through the mystery of a new plant. No wonder Linnaeus loved his method. He studied thousands of different kinds of plants; the sexual system represents the life-experience of one of the most brilliant field-botanists who ever lived. In using the sexual system to guide our study of many different plants at a single setting, we stepped right into Linnaeus's times and challenges. His system worked, quickly and intelligibly. It proved to be a great teaching method, bringing novices quickly into an appreciation of plant structure and diversity. Working through flowers from Linnaeus's perspective is wonderfully enlightening, engaging, and worthwhile.

But that doesn't mean there are publishable results. The system has serious limits. It gets you to a place in a list or chart, but it doesn't reckon on today's reality - the sheer number of different kinds of plants we have come to understand there are and have been on Earth. Linnaeus's system suggests a matrix of potential structural combinations, which would mean our discovery of plants would have yielded less than 50,000 kinds. He thought all the world's plants would be known in short order. That did not happen, and with over 250,000 accepted species, we continue to add new kinds. And, honestly, there is nothing that Linnaeus's system brings to the table in a contemporary understanding of plant affinities or evolution.

But for students who want to learn more plants, and more about plants, Linnaeus's methods have much to offer. Following his system gives the student of plants access to Linnaeus's approach to making sense of the great range of plant diversity - an approach molded through experience and a genius for comprehending and organizing the breadth of creation.