OVULATE CONE, POLLINATION DROP, AND POLLEN CAPTURE IN SEQUOIADENDRON (TAXODIACEAE)

In Sequoiadendron ovules are borne inside the ovulate cone, and pollin ation drops secreted from these ovules collect pollen. We examined: (1 ) the relation between ovular position and pollen capture; (2) pollen behavior when in contact with a pollination drop; and (3) ultrastructu re of ovules during pollination drop secretion. During wet periods a w ater sheet forms on the surface of the cone due to bract shape and wet tability. Pollination drops persist inside the wetted cone, and pollen capture resumes immediately after drying. Pollen landing on a pollina tion drop is taken inside the drop and carried into the micropyle when the drop contracts. Several notable ultrastructural features appear i n the nucellus, integument, chalaza, and bract lamina during pollinati on-drop secretion. The abaxial surface of the lamina is covered by a m embrane that may contribute to the wettable nature of the surface.