Explanation:

- Matthias Schleiden:

- The correct answer.

- In 1838, Matthias Schleiden published an article on the structure and origin of plant cells.

- He was a German botanist and co-founder of cell theory.

- Robert Brown:

- Known for discovering the cell nucleus.

- Did not publish on plant cell structure and origin in 1838.

- Rudolf Virchow:

- Known for stating "Omnis cellula e cellula" (every cell from a cell).

- Published his work on cellular pathology later, not in 1838.

- Albert von Kölliker:

- Not associated with the 1838 publication on plant cell structure.

- Known for his work in histology later in the 19th century.