Answer:
1938
Explanation:
Matthias Schleiden was a German botanist who studied the plant's cell and its structure under the microscope. In 1938 he contributed to the cell theory and stated that every tissue present in the plant is made of or cells and an embryonic plant is produced from one single cell.
In 1939 another scientist Theodor Schwann proposed the same conclusion after studying animal cells and concluded that the basic unit of life is cell and every organism on earth is made up of one or more cells. Therefore Theodor Schwann and Matthias Schleiden have great contribution in cell theory.
