“…As a result, a number of evolutionary trends have been hypothesized for the reproductive morphology of the family, and especially for Azolla (e.g., Fowler, 1975;Martin, 1976;Collinson, 1980;Saunders and Fowler, 1993). It has generally been accepted, and recently restated, that one of the trends in hydropteridinean megaspores has been the reduction in float number (e.g., Jain and Hall, 1969;Hall and Bergad, 1971;Jain, 1971;Hall, 1974;Saunders and Fowler, 1993). This idea is based on the fact that modern representatives of Azolla have few floats, while many fossil genera such as Glomerisporites, Azollopsis, and several extinct sections of Azolla have numerous floats.…”