SummaryAugust Schleicher’s genealogical tree (Stammbaum) and Johannes Schmidt’s wave metaphor (Welle) are very well known linguistic concepts. At the same time there has been a widespread misunderstanding about their original meaning and the questions they were intended to deal with. Both were originally classificatory concepts, not models of language change. Schleicher, on the one hand, introduced theStammbaumby transforming hierarchical classes of Indo-European languages into successive historical stages. Schmidt, on the other hand, rejected the idea of subgrouping Indo-European languages as required by Schleicher’sStammbaum. Instead, he assumed an original continuum of languages. He described this continuum metaphorically in terms of concentric ‘waves’. The interpretation of the wave image as a metaphor for the geographical spread of linguistic innovations (as has become common) is the result of later adaptations in dialectology.