Structure and Function of Transfer Cells in the Sporophyte Haustorium ofFunaria hygrometricaHedw

The development of the sporophyte-gametophyte interface in the moss, Funaria hygrometrica Hedw., is described with the aid of light- and electron-microscopy. The outer walls of the cells that abut the haustorial cavity in both generations develop labyrinths typical of transfer cells. This feature is more apparent in the epidermal cells of the sporophyte foot (haustorium), where development can be split into three main stages. The primary growth stage, which is complete at about the time the calyptra detaches from the ripened archegonium, involves the formation of transfer cells. The secondary stage is characterized by the deposition of amorphous inclusions in the wall labyrinth of the transfer cells. The tertiary stage, which commences as the sporophyte capsule ripens, entails de-differentiation of the transfer cell wall labyrinth to form a thick, heavily encrusted, outer cell wall. The pattern of development of these cells is correlated with changes in gametophyte- sporophyte translocation capabilities.