Perforation plate pit membrane remnants in vessels of Sarraceniaceae: Possible indicators of relationship and ecology

All three genera of Sarraceniaceae possess pit membrane remnants in perforations: the abundance of pit membrane remnants parallels the number of bars per perforation plate: most in Heliamphora, fewer in Sarracenia, fewest in Darlingtonia. Heliamphora perforation plates were reported earlier, so Darlingtonia (monotypic) and two species of Sarracenia are considered here. The majority of perforations lack extensive pit membrane remnants, but occasional meshwork-like remnants can be seen at the lateral ends of a number of perforations. Perforations intermediate in size and morphology between perforations and lateral wall pits (pit membranes nearly intact, but containing numerous pores) often occur at upper and lower ends of perforation plates. Pit membrane remnants of this type have been reported in scalariform perforation plates of families thought to be closely related to Sarraceniaceae (Clethraceae, Cyrillaceae, Ericaceae). Species of all four families in which pit membranes are present occur in highly mesic or bog habitats.