August Schleicher began his career studying theology and Indo-European, especially Slavic languages. Influenced by Hegel, he formed the theory that a language is an organism, with periods of development, maturity, and decline. In 1850 Schleicher completed a monograph systematically describing the languages of Europe, Die Sprachen Europas in systematischer Übersicht (The languages of Europe in systematic perspective). He explicitly represented languages as perfectly natural organisms that could most conveniently be described using terms drawn from biology e.g., genus, species, and variety.
Schleicher claimed that he himself had been convinced of the natural descent and competition of languages before he had read Darwin’sOrigin of Species. He invented a system of language classification that resembled a botanical taxonomy, tracing groups of related languages and arranging them in a genealogical tree. His model, the Stammbaumtheorie (family-tree theory), was a major development in the study of Indo-European languages. To show how Indo-European might have looked he created a short tale, Schleicher's fable, to exemplify both words and known culture. He first introduced a graphic representation of a Stammbaum in articles published in 1853. By the time of the publication of his Deutsche Sprache (German language) (1860) he had begun to use trees to illustrate language descent. Schleicher is commonly recognized as the first linguist to portray language development using the figure of a tree.
Sprachvergleichende Untersuchungen. / Zur vergleichenden Sprachgeschichte. (2 vols.) Bonn, H. B. Koenig (1848)
Linguistische Untersuchungen. Part 2: Die Sprachen Europas in systematischer Uebersicht. Bonn, H. B. Koenig (1850); new ed. by Konrad Koerner, Amsterdam, John Benjamins (1982)
Formenlehre der kirchenslavischen Sprache. (1852)
Die ersten Spaltungen des indogermanischen Urvolkes. Allgemeine Zeitung fuer Wissenschaft und Literatur (August 1853)
Handbuch der litauischen Sprache. (1st scientific compendium of Lithuanian language) (2 vols.) Weimar, H. Boehlau (1856/57)
Litauische Maerchen, Sprichworte, Raetsel und Lieder. Weimar, H. Boehlau (1857)
Volkstuemliches aus Sonneberg im Meininger Oberlande - Lautlehre der Sonneberger Mundart. Weimar, H. Boehlau (1858)
Kurzer Abriss der Geschichte der italienischen Sprachen. Rheinisches Museum fuer Philologie 14.329-46. (1859)
Die Deutsche Sprache. Stuttgart, J. G. Cotta (1860); new ed. by Johannes Schmidt, Stuttgart, J. G. Cotta (1888)
Compendium der vergleichenden Grammatik der indogermanischen Sprachen. (Kurzer Abriss der indogermanischen Ursprache, des Altindischen, Altiranischen, Altgriechischen, Altitalischen, Altkeltischen, Altslawischen, Litauischen und Altdeutschen.) (2 vols.) Weimar, H. Boehlau (1861/62); reprinted by Minerva GmbH, Wissenschaftlicher Verlag, ISBN 3-8102-1071-4
Die Darwinsche Theorie und die Sprachwissenschaft - offenes Sendschreiben an Herrn Dr. Ernst Haeckel. Weimar, H. Boehlau (1863)
Die Bedeutung der Sprache für die Naturgeschichte des Menschen. Weimar, H. Boehlau (1865)
Joachim Dietze: August Schleicher als Slawist. Sein Leben und Werk in der Sicht der Indogermanistik. Berlin, Akademie Verlag (1966)
Konrad Körner: Linguistics and evolution theory (Three essays by August Schleicher, Ernst Haeckel and Wilhelm Bleek). Amsterdam-Philadelphia, John Benjamins Publishing Company (1983)
Liba Taub: Evolutionary Ideas and "Empirical" Methods: The Analogy Between Language and Species in the Works of Lyell and Schleicher. British Journal for the History of Science 26, S. 171-193 (1993)
Theodeor Syllaba: August Schleicher und Böhmen. Prague, Karolinum (1995). ISBN 807066942X