As in other epiphytic species
(Withner, et al., 1974), the outer velamen layer
has hairs in the root of Pleurothallis smithiana
(Fig. 4); in this root the suberized thickening,
observed between the two cellular layers of the
velamen (Fig. 5), were absent in the contact
region with root hairs. Such absence could be
related to the efficiency of the absorptive
process.