Abstract With most species of the Ophioglossaceae, gametophyte development and maturation are slow and some species have perennial gametophytes. A few species, including O. crotalophoroides, appear to have gametophytes that mature rapidly. To determine how fast the gametophytes of this species mature, they were grown in axenic culture. The early sequence of cell divisions following germination is the same as for other species of the Ophioglossaceae. The formation of mucilage on the proximal cell of the young gametophyte and on the rhizoids of older gametophytes has also been reported for other members of the family. The spores of O. crotalophoroides have the second fastest germination, 8 days, for this family. Gametophytes of this species grow faster than gametophytes of two Botrychium species. The gametangia form on smaller gametophytes of O. crotalophoroides than on those of Botrychium. Rapid spore germination, rapid gametophyte growth, and smaller gametophyte size at maturity all contribute to the formation of sexually mature gametophytes in 6.5 months. This is the fastest gametophyte maturation reported for the family.