Xerophytes, xeromorphs and sclerophylls: the history of some concepts in ecology

Research on xeromorphic and sclerophyllous (the literal meanings of which are dry-form and hard-leaved) plants offers a case-history illustrating the nature of progress in one branch of science. The story runs from about 1890–1970, beginning with the birth of ecological concepts, including Warming's 1895 classification of plants into hydrophytes, xerophytes and meso-phytes, Schimper's pioneer work on the sclerophylls, and with the conceptions that lay behind this work; and so on through the main lines of research, concluding with an account of work on the anomalous distribution of the sclerophylls in Australia. This case-history shows how the problems of classification and categorization may be linked to conceptual and empirical problems of substance, and hence are not merely classificatory. Indeed, the hypotheses under test are not formulated explicitly, but are encapsulated in the terminology, as is so often the case in the biological sciences.