The Trentepohliaceae were characterized in the past as having a central pit in the transverse walls. EM shows the pit to be a group of plasmodesmata rather than a single large plug like that of red to be algae. A cultured species of Cephaleuros with narrow filaments and narrow transverse walls has plasmodesmata occupying nearly the entire transverse wall. Collected Cephaleuros spp. found on the leaves of Magnolia and other woody genera have wider transverse walls with plasmodesmata centrally located in a pit. A cultured species of Trentepohlia with cell width intermediate between the 2 types of Cephaleuros has plasmodesmata centrally located in a pit, but the pit occupies a large portiolnof the transverse wall. The Trentepohliales can be characterized as possessing a centrally located in a pit, but the pit occupies a large portion of the transverse wall. The Trentepohliales can be characterized as possessing a centrally located group of plasmodesmata, but they are clearly seen as such only in wider cells where the transverse wall extends sufficiently beyond the central region. Some taxonomic, developmental and phylogenetic problems are discussed.