Von Naegeli

Naegeli, Carl Wilhelm von

OTHER-NAME:

BIRTH: 27 March 1817; Kilchberg, nr Zurich, Switzerland

DEATH: 10 May 1891; Munich, Germany

CATEGORY: Science

DISCIPLINE: Botany

ASSESSMENT: He was in influential figure in encouraging the detailed examination of cell division in relation to plant development and the process of evolution.

LANGUAGE: German

EDUCATION: Zurich Gymnasium; Zurich University; Geneva University

ACHIEVEMENT: He made a major contribution to the understanding of cell behavior

MAJOR-WORK: The mechanico-physiological theory of evolution (1884)

PARENTS: His father was a doctor.

SPOUSE:

SIBLINGS:

CHILDREN:

DETAILS: Stimulated by the lectures on zoology by Oken*, a proponent of naturphilosophie*, in 1839 Naegeli gave up medicine at Zurich to study botany under Candolle* at Geneva, and graduated with a botanical thesis at Zurich in 1840.

He spent that summer in Berlin reading the work of Hegel*. In 1842 he moved to Jena, where he worked under professor of botany Matthias Schleiden*, who had recently become famous for his theory of cell formation.

In 1852 he was given the chair of botany at the university of Frieberg im Breisgau and in 1857 promoted to professor at Munich where he remained until his death.

Naegeli was profoundly influenced by Schleiden’s theory of cell formation and he dedicated his life to the study of animal and plant cell growth.

In spite of denying Hegel’s influence, Naegeli looked for universal laws to apply to the behavior of the cell and sought ways of expressing this in mathematical terms. In 1842 he wrote a paper on pollen formation of seed and flowering plants and gave the first detailed description of cell division, in which he noted that the cell wall formed between daughter cells was the result of and not the cause of division

He described what he called ‘transitory cytoblasts,’ later were identified as chromosomes. He also investigated the process of osmosis in single-cell algae. In 1844 he discovered the reproductive structures in which male fern sex cells develop.

Naegeli introduced the botanical concept ‘meristem’ (a group of plant cells capable of division and responsible for plant growth). This led him to the first accurate description of apical cells (found in the root and shoot tips, and the initial point of longitudinal growth in plants).

In 1858 he demonstrated the importance of the sequence of cell division in the formation of plant parts and theorized that because of the time it took for complexity to develop, simple structures must be younger than complex ones.

During studies of starch, he proposed a unit of structure he named the ‘micelle,’ a building block, set in a crystal-like array and made up of nearly nine thousand molecules. Water could penetrate the spaces between micelles, and new micelles could form in those spaces. This, Naegeli thought, might be the mechanism by which cell walls grew, too. His description of micelles kicked off a generation of German and Swiss botanical work on fine structure in cells.

Naegeli (and Hugo von Mohl, a German botanist) were the first to distinguish the plant cell wall from the inner cell contents, which von Mohl named ‘protoplasm’ in 1846. Naegeli believed that cells received their hereditary characters from a part of the protoplasm which he called ‘idioplasma.’

Naegeli did not accept environmental factors acting to produce variations in species, believing instead that evolution occurred in jumps (in this way possibly anticipating the discovery of mutation).

According to Naegeli, species variation was caused internally by a force that drove evolutionary changes in a particular, ‘higher’ direction, such as increased size and complexity. Each organism was, in this sense, an advance on its predecessor.

Natural selection and adaptation, such as that proposed by Darwin*, had for Naegeli only a minor effect on the evolution of organisms.

This view led him to reject a paper on the laws of inheritance sent him by Mendel*. Ironically, Naegeli’s student Correns* would be one of those who would later rediscovered and promote Mendel’s laws and help establish the filed of genetics.

EXTRA-CONNECTIONS: He was succeeded in Freiberg by De Bary*

He taught Vierordt*

ONELINER: Carl von Naegeli, nineteenth century Swiss botanist

BIBLIOGRAPHY:

Dictionary of Scientific Biography

Encyclopedia Britannica