A botanist who proposed the cell theory was:

Explanation

The cell theory, a fundamental principle in biology, was proposed by Matthias Schleiden and Theodor Schwann. Schleiden, being a botanist, focused on plant cells and their structure, contributing to the theory's formulation. While Schwann also contributed significantly, he was a zoologist. Robert Hooke's work was pivotal in cell observation, but not in theory formulation, and Robert Brown's discovery of the nucleus was a separate contribution to cell biology.