Survey of Intervessel Pit Membrane Structure in Daphne Species

Abstract

Of 22 species of Daphne surveyed, 19 possessed tori in their intervessel pit membranes. The torus has a circular shape and is centrally-located on the pit membrane. The fibrils of the surrounding margo show a random arrangement. In some specimens, the fibrils are obscured by material that impregnates the margo, coats the torus, and lines the cell lumens. The margo has small pores. In those species without tori, the intervessel pit membranes, when intact, show randomlywoven fibrils and small pores. Air-dried membranes of these speeies tend to separate into two layers along the line of the middle lamella The presence of a torus is not correlated with evergreen or deciduous habit, but absence of a torus seems to be limited to species of the section Mezereum within the genus Daphne .