Matthias Jacob

He became professor of botany at the University of Dorpat in 1863. He concluded that all plant parts are made of cells and that an embryonic plant organism arises from the one cell.

Schleiden was an early advocate of evolution. In a lecture on the "History of the Vegetable World" published in his book The Plant: A Biography (1848) was a passage that embraced the transmutation of species. He was one of the first German biologists to accept Charles Darwin's theory of evolution. He has been described as a leading proponent of Darwinism in Germany.

He soon developed his love for botany into a full-time pursuit. Schleiden preferred to study plant structure under the microscope. As a professor of botany at the University of Jena, he wrote Contributions to our Knowledge of Phytogenesis (1838), in which he stated that all plants are composed of cells. Thus, Schleiden and Schwann became the first to formulate what was then an informal belief as a principle of biology equal in importance to the atomic theory of chemistry. He also recognized the importance of the cell nucleus, discovered in 1831 by the Scottish botanist Robert Brown, and sensed its connection with cell division.

He studied natural science at the University of Göttingen in Göttingen, Germany, but transferred to the University of Berlin in 1835 to study plants. Johann Horkel, Schleiden's uncle, encouraged him to study plant embryology.

Matthias Jakob Schleiden was born in Hamburg, a city of the Holy Roman Empire, on 5 April 1804. His father was the municipal physician of Hamburg. Schleiden pursued legal studies graduating in 1827. He then established a legal practice but after a period of emotional depression and an attempted suicide, he changed professions.