Matthias Schleiden

Matthias Jakob Schleiden (5 April 1804 23 June 1881) was a German botanist. He was long supposed to be the co-founder of the cell theory, with Theodor Schwann and Rudolf Virchow. However, a recent study of the original papers revealed that Schleiden and Schwann used previous research, and were popularisers of an idea others had discovered.
Modern assessment.
The earlier work of the Czech Jan Purkyně (1787–1869) and his student and collaborator Gabriel Valentin (1810–1883) was "unjustly denigrated by the nationalistic Germans. They have a claim to some priority in the cell theory".Chapter 9
Johannes Müller (1801–1858) also made great contributions. It was, however, his student Theodor Schwann and Matthias Schleiden who got the credit for the cell theory. This was despite the fact that some of their observations were not correct, and their credits to previous workers were "a travesty".p97 As understood now, the cell theory includes these important ideas:
The key works of Schwann and Schleiden were published in 1838 and 1839.
These ideas still are the basic ideas of cell theory.