Asa Gray never expanded his knowledge of floristic bryology to the extent he developed expertise in flowering plant taxonomy. Nevertheless, he became experienced in bryological floristics early in his botanical career, and Gray absorbed new bryological information, both floristic and conceptual, throughout his life from wherever it was generated. He had plans to advance bryology in the United States, including an exsiccata and publishing a volume devoted to cryptogams as part two of the second edition of his Manual, but both never happened. His respect for the bryological talent and energy of William S. Sullivant, whose achievements Gray consistently encouraged and fostered, allowed Sullivant, a non-academic in Columbus, Ohio, to become a highly regarded bryologist of international stature and the designated Father of American Bryology. The growth of bryofloristic knowledge in the United States is traced from the earliest colonial period to later workers, including Dillenius, André Michaux, Palisot de Beauvois, Henry Muhlenberg, Lewis Schweinitz, Lewis Beck, and John Torrey, to Asa Gray, and eventually to William Sullivant. The bryological work and accomplishments of each of them show that all participated in a sophisticated international network of information exchange by letter or other conveyance, thereby building important collections of bryophyte specimens and printed references. For some, this happened during the 1800s when improvements in compound light microscopy led to the resolution of morphology not before revealed with certainty in bryophytes and to conceptual advances in understanding the biology of these plants, which in turn allowed the discovery of the mesoscale structural uniqueness of them and continuing advancements in their systematics in the post-Sullivant era.