Hugo von Mohl

1805-1872

German Botanist

German botanist Hugo von Mohl was one of the first to use the microscope to study the nature of plant cell structure and the physiology of higher plants. He is credited with recognizing and naming protoplasm and proposing that cells divide to form new cells.

Born in Stuttgart, Germany, on April 8, 1805, Mohl was part of a respected middle-class family who placed a great deal of value on scholarship. Brother Jules became a naturalized Frenchman and professor of Persian. Two other brothers were respected in the fields of economics and politics. However, from an early age Mohl's interest was science, especially botany and optics. He had a happy childhood and adolescence, and his university career and personal life were pleasant with few difficulties.

Mohl received a doctor of medicine at Tübingen in 1828. Interest in the puzzling mystery of climbing plants led to a doctoral dissertation on the stomata, or pores, in the leaves of plants. In 1832 he was given a post as professor of physiology at Bern, and in 1835 became a professor of botany at Tübingen, a position he held until his death.

The hobby of working with lenses and the microscope turned out to be a major focus of his vocation. He continued to develop and improve the microscope and wrote a how-to manual on the subject in 1846.

With the microscope, he determined that the basic structure of the cell included movement within, referred to as intracellular movement. He was the first to develop the idea that there is a nucleus within the granular flowing material that forms the main substance of the cell, naming this substance "protoplasm." This term, meaning "first form," was coined by Czech physiologist Jan Evangelista Purkinje (1787-1869) to refer to the embryonic material found in eggs. Mohl's application of the word was adopted into the knowledge of the time and survives as part of biology today. Protoplasm, a semi-fluid colloid, is the matter of life in all plant and animal cells.

Mohl's meticulous studies revealed the first description of the division of cells. Observing division of the alga Conferva glomerata, he recognized the tough secondary fibrous substance of the plant now known as the cell wall. In 1853 he published a very important work, Die vegetabilishe Zelle (The Plant Cell), which became a classic work in botany. The book presented a panorama of what was known about botany. He took the cell as the base, calling it "an elementary organ."

Mohl was very specific in his concrete descriptions and did not draw general conclusions from speculative thought. He appreciated the critique of his work by colleagues and contemporaries.

Among his varied scientific contributions were the discovery of the nature of small bodies within specialized cells, called plastids, and the process of osmosis, the passage of molecules through a membrane from a place of high concentration to low. He identified the stomata, the openings in leaves where carbon dioxide and water are taken in and oxygen is given off.

Mohl never married and did not consider it important to have a circle of friends or admiring students. Skill with his hands, meticulous work habits, and attention to detail brought him great satisfaction and recognition. He was one of the founders of Botanishe Zeitung (Botany Times), a prestigious journal that still exists today. His desire for outstanding science education for students led to the creation of the Faculty of Sciences at Tübingen, one of the first of its kind. He received many honors, including the Order of Wurtenberg in 1843 and an accompanying title of nobility. Mohl died in his sleep on Easter Sunday, April 1, 1872.

EVELYN B. KELLY