THE SCIENCE OF PLANT MORPHOLOGY: DEFINITION, HISTORY, AND ROLE IN MODERN BIOLOGY 1 THE SCIENCE OF PLANT MORPHOLOGY (original) (raw)

As a scientific discipline, plant morphology is 211 yr old, originated by Goethe in 1790. It is a discipline that has largely been Germanic in practice. Because it took its origins from the study of the natural history of plants and the United States is principally an engineering society, the discipline of plant morphology in its pure form has never been widely practiced in this country. What has been labeled ''plant morphology'' in the United States has served largely as a handmaiden for systematics, using morphological characteristics to carve up diversity into its systematic subunits. Because the heart of plant morphology as a science is a focus on the convergences rather than the homologies in a phylogenetic sense, the German tradition of plant morphology is a unifying science that focuses on fundamental themes that transcend systematic boundaries. This paper traces the history of the science of plant morphology through the lineage of its principal practitioners: Goethe, Hofmeister, von Goebel, and Troll. It also evaluates the principles of plant morphology by applying them to the phyletically diverse Pteridophytes, showing that contemporary members of that group exhibit levels of shoot organization comparable to that of seed plants and discusses the implications of these findings. Although the Pelton Award is made for meritorious work in the field of experimental morphology of plants, I consider the latter as a particular approach within the broader and older discipline of plant morphology. In recent times there has been no clear statement of what the science of plant morphology is and how such emphases relate to the science as a whole. It is not clear to many practitioners that plant morphology itself represents a valid scientific discipline. Due to historical declines in the interest and teaching of plant morphology, it has come to be viewed largely as a provider of characters for systematic circumscription, hence virtually synonymous with plant systematics. Given that contemporary systematics has put a greater emphasis on molecular rather than morphological data, the time seems ripe to reevalute plant morphology and what its role can and should be in modern plant biology. In this article I attempt to clarify the concept of plant morphology as a discipline, review its historical heritage, and discuss how it relates to and differs from systematics. I show that plant morphology is a scientific discipline with its own principles , from which predictions can be made about the unknown. I illustrate some of these general principles and their application by evaluating them in a phyletically heterogeneous plant group, the pteridophytes, which previously had been interpreted largely by models from fossil rather than contemporary plants. The principal reasons the science of plant morphology is virtually unknown and did not make an impact in the Anglo-American regions of the world are mainly cultural and historical. Plant morphology is largely a German science that never was prominent in the United States. The German tradition of plant morphology took its origins from the study of the natural history of plants. Because the United States is principally an engineering society, concerned more with the tools of science than with its theory, philosophy, and history, we have never had a comparable natural history tradition. Because it required the use of a particular tool (microscopy), plant anatomy, which focuses on the cell and tissue levels of organization, received greater emphasis and scientific credibility in this country than did plant morphology. This difference in emphasis is reflected especially in the difference in conception of what has been called ''plant morphology'' in the United States compared to this concept in Germany. Following the tradition established by Coulter and Chamberlain of the University of Chicago (Coulter and Chamberlain, 1901), plant morphology in the United States was defined as the study of the anatomical and cytological features of the life histories of plants expressed in a taxonomic framework. Hence, the emphasis was on the microscopic details of vascular plant reproduction and systematic relationships with the focus of the German tradition relegated to brief accounts of the plant's habit. In the context of our country's emphasis on tools and techniques rather than philosophy, this microscopical/life-history conception of plant morphology doubtless was seen as being more rigorous than the seemingly less precise study of form relationships based on external morphology, i.e., the German tradition. A series of influential textbooks exemplifying and promoting this Anglo-American conception of plant morphology developed through the years, including the most recent editions of Bold, Alexopoulos, and Delevoryas (1987); Gifford and Foster (1989); and Scagel et al. (1984). These works not only reinforced this life-history emphasis in research and ped