Matthias Jakob Schleiden

Die Entwickelung der Meduse ("The Development of the Medusas"), in Schleiden's Das Meer

Matthias Jakob Schleiden (April 5, 1804 - June 23, 1881) was a German botanist and co-founder of cell theory. He was born in Hamburg, Germany. Schleiden was educated at Heidelberg and practiced law in Hamburg but soon developed his hobby of botany into a full-time pursuit. Schleiden preferred to study plant structure under the microscope. While as professor of botany at the University of Jena, he wrote Contributions to Phytogenesis (1838), in which he stated that the different parts of the plant organism are composed of cells. Thus, Schleiden 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. Schleiden was one of the first German biologists to accept Charles Darwin's theory of evolution. He became professor of botany at the University of Tartu (then Dorpat, in what is today Estonia) in 1863.

The standard botanical author abbreviation Schleid. It is applied to species he described.

References

He also once dined with Theodor Schwann. Edit this if I'm wrong, but they came across the subject of the nuclei of plants. That was when Schwann suddenly had the idea that animals and not only plants were made of cells.