As Chapter 17 makes clear, the asexualist/sexualists controversy continued even as Johann Hedwig and Karl von Nägel demonstrated the existence of sex in cryptogams by discovering the Alternation of Generations (1782, 1784), hybridizers A. F. Wiegman and Carl Friedrich von Gaertner recieved prestigious prizes for their work, and Giovanni Battista Amici and Adolphe-Theodore Brongniart discovered—and confirmed—the pollen tube. Unconvinced, Matthias Jacob Schleiden, co-founder of the cell theory, insisted that ferns grow asexually from spores, and that spores, not seeds, are the primary units of propagation in seed plants also. He argued (1853) that the entire life-cycle of seed plants is based on duplicative cell divisions that produce seeds entirely by vegetative processes. Following the Aristotelian doctrine that the female parent provides the material substance of the embryo, he concluded pollen must be a female structure that reproduces vegetatively—thus making the case for a unisexual, plants-as-female model.
On Apogamy and the development of Sporangia upon fern prothalli