Simulated wind pollination and airflow around ovules of some early seed plants.

Scale models of various early seed plant ovules and cupules were analyzed both for their characteristic air disturbance patterns and for the frequency of impact with airborne models of pollen (pseudopollen). The fossils on which the models were based had been arranged in an evolutionary sequence purporting to show the origin of the integument by the acropetal fusion and reduction in length of a subtending truss of lobes. Wind tunnel analyses of scale models showing the various stages in the consolidation of these preintegumentary lobes indicated that turbulent flow increases and becomes localized around the nucellar apex (salpinx) with the syngenesis and length reduction of those lobes. Similarly, the frequency of windborne pseudopollen impact increased. Thus, the transition from the megasporangium to the fully integumented ovule appears to favor increased wind-mediated pollination.