Seed morphology has been an important taxonomic character for the Bromeliaceae, with three distinct seed types, naked, winged, and plumose, corresponding to the traditionally recognized subfamilies, Bromelioideae, Pitcairnioideae, and Tillandsioideae, respectively. In Tillandsioideae, the type of plumose seed appendage is used, in conjunction with other characters, to help circumscribe genera. For example, Catopsis, a genus of approximately 20 species, is characterized by having an apical coma of hairs, in contrast to Guzmania, Vriesea, and Tillandsia where seeds have a basal coma of hairs. The individual hairs, apical or basal, that comprise the plumose coma of the Tillandsioideae seeds have been assumed to be homologous structures. Scanning electron and light microscopy were used to examine the details of seed hair development in representative species of Catopsis and Tillandsia. Observations made in this study confirm published details of the basal seed hair development for Tillandsia. The apical seed hairs characteristic for Catopsis are shown to have a distinctly different ontogeny, and are judged to be synapomorphic for the genus. The apical and basal plumose seed appendages diagnostic for subfamily Tillandsioideae are analogous, but are not homologous in the ontogenetic or positional sense.