Klebs, Georg Albrecht

(b. Neidenburg, Germany, 23 October 1857; d. Heidelberg, Germany, 15 October 1918)

botany.

Klebs was the third son of Emil Klebs, a Prussian Consistory Councillor. He received his education in the small East Prissian city of Wehlau, entering elementary school in 1864 and graduating from the Realgymnasium in 1874. He then studied the natural sciences, philosophy, and art history at the University of Köonigsberg. During his first semester he composed a prize essay in philosophy; but in preparing a study of the Desmidiaceae, an algae family, his interest was drawn to botany. This work (1879) brought him a position as an assistant to Anton de Bary at the University of Strasbourg (1878-1880). Subsequently he became an assistant to the leading plant physiologists of the time, Julius Sachs at Wüurzburg and Wilhelm Pfeffer at Tüubingen. In 1883 he qualified as lecturer at Tüubingen. Klebs was appointed a full professor at Basel in 1887 and obtained the same position in 1898 at Halle and in 1907 at Heidelberg, where he was simultaneously named privy councillor. In 1913 he received the Knight’s Cross of the Zäahringer Löowen. Klebs was rector of the University of Basel for a year and twice dean of the Science and Mathematics Faculty at Heidelberg. Shortly before his death he was elected rector of the University of Heidelberg . He was a member of many scientific academies. On 20 March 1888 he married Luise Charlotte von Sigwart of Tüubingen; they had three children.

In his scientific work, which was stimulated primarily by de Bary, Klebs at first concentrated on systematics among the algae and fungi, but he soon turned his attention to the cellular and reproductive physiology of these plants. His important discoveries in these areas include the fact that the presence of the nucleus is necessary for the formation of a cell wall.

Klebs’s principal work began with his extensive investigations of developmental variation among both lower and higher plants, particularly of the way in which variation is brought about through alteration of environmental factors. This research was set forth in two books that appeared in 1896 and 1903. Starting with his first works in this field, Klebs not only presented interesting facts but also furnished, through suitable definitions, the correct points of departure for mastering developmental physiology through experimentation. This was his most lasting achievement. Specifically, he was the first to make a logically consistent division of the influences affecting development into external conditions, internal conditions, and specific structure. He defined their combined activity as follows: “All variations of [a species] are generated by the external environment in that it materializes, through its effect on the inner conditions, the powers lying dormant in the specific structure” (“Uber das Verhäaltnis der Aussenwelt zur Entwicklung der pflanzen,” p. 12). The crucial innovation of this conception is the distinction between the unchangeable specific structures (the genetic endowment) of the cell and the internal factors that are altered in response to external conditions. Klebs demonstrated the validity of this point of view in many experiments on fungi, ferns, and flowering plants. Moreover, with this definition he gave developmental physiology its own methodology and was thus its real founder.

Although Klebs’s view was accepted only hesitantly—undoubtedly because of certain errors it contained, including the belief that it is not necessary to distinguish between mutations and variations—many contemporaries praised him unreservedly.

The full importance of Klebs’s conception could not be appreciated, however, until the “arbitrary,” and therefore often indiscriminate, developmental variations which he had posited were replaced by regular variations.

BIBLIOGRAPHY

I. Original Works. A complete bibliography of Klebs’s writings can be found in Küster (see below). They Uuml;ber die Fortpflanzungsphysiologie der niederen Organismen der Protobiontenn . . . (Jena, 1903); and “Uuml;ber das verhältnis der Aussenwelt zur Entwicklung der Pflanzen. Eine thoretische Betrachtung,” in Sitzungsberichte der Heidelberger Akademie der Wissenschaften, Sec. B. (1913), 5th essay, 1-47.

II. Secondary Literature. On Klebs or his work, see M. Bopp, “Georg Klebs und die heutige Entwicklungsphysiologie,” in Naturwissenschaftliche Rundschau, 22 (1969), 97-101; E. Küster, “Georg Klebs 1857-1918,” in Berichte der Deutschen botanischen Gesellschaft, “Uuml;ber den rhythmischen Wechsel von Wachstum und Ruhe bei den Pflanzen,” in Biologisches Zentralblatt, 35 (1915), 401-471; G. Melchers, “Einführung” in W. Ruhland, ed., Handbuch der pflanzenphysiologie, XVI (Berlin-Götting-Heidelberg, 1961), xix-xxvi; and E. Ungerer, “Die Beherrschung der pflanzlichen Form. Eine Einführung in die Forschungen von Georg Klebs,” in Naturwissenschaften, 6 (1918), 683-691.

M. Bopp