| One of the most innovative theories of nineteenth-century biology asserted that the cell was the unit of life: each moss or tree, jellyfish or human being was actually made up of microscopic individual organisms—cells. How did this understanding of the relationship of parts and wholes in living things develop? What were the questions to which cell theory was the answer? Traditional histories have tended to look narrowly at observations of cells and theories of micro-units. Yet before the cell theory, researchers subsumed cells within broader treatments of organismal form, growth, and generation. I show how the rich tradition of botanical work on morphology, development, reproduction, nutrient processing, and the relationship of macroscopic subunits to the whole all contributed to the cellular vision of life. Summarizing Johann Wolfgang von Goethe, Alexander von Humboldt, Caspar Friedrich Wolff, and others, I begin with eighteenth-century treatments of topics that would frame the researches of some early nineteenth-century cell theorists: sap and tissue formation, alternatives to sexual mixture, the kinship of reproduction and growth, buds as individuals, and the morphological quest for unifying principles that transcended the diversity of life. Only in the 1820s and 1830s did the focus begin to shift to the cell. Henri Dutrochet and Franz Julius Ferdinand Meyen added the bounded and active cell to traditional theories of sap flow and tissue formation. Asking a separate set of questions about generation, Matthias Jacob Schleiden built on the findings of Robert Brown to create a radical new theory of homologies between phanerogam pollen and cryptogam spores, and to integrate cell individuality into developmental morphology. |
