Unusual pit membrane remnants in perforation plates of Cyrillaceae

Pit membrane remnants occur in all collections of Cyrillaceae studied: they are minimal in Cliftonia monophylla, C. parviflora, and Purdiaea antillana, whereas in the specimen of Cyrilla racemiflora, many perforations possess intact pit membranes or membranes with small pores or, in a few cases, large holes. Some perforation pit membranes in C. racemiflora appear to possess holes only in one of the two pit membranes of the two adjacent cells. Retention of pit membrane remnants in C. racemiflora may represent a tendency to lose conductive capability related to the habitat (understory, marshy ground) This could be considered a stage in vessel loss except for the fact that three other criteria for vessel loss are not met. Presence of pit membrane remnants in Cyrillaceae is consistent with such presence in the sister family Clethraceae as well as in other families of Ericales (Theales of some authors) as defined on the basis of recent molecular data.