Bordered pit pairs connecting tracheary elements in the wood of Osmanthus americanus (L.) Benth. ' Hook. ex Gray contained a torus in the pit membrane. This structure is approximately 2.5 μm in diameter, and is located at or near the centre of the pit membrane. The encrusting material of the torus could be removed by treatment with sodium chlorite. Thin seetions through theJorus showed it to consist of a pad of wall material appressed to either side of the compound middle lamella. The membrane surrounding the torus (the margo) consisted of fibrils and a variable amount of enc10sing matrix. The fibrils were generally c1oseIy packed and randomly oriented, although occasionally a radial component was also present. Aspiration of the pit membrane in air-dried material caused the torus to seal off one of the pit apertures. During this process the torus probably prevented rupture of the pit membrane at that site.