The largely tropical Podostemaceae occur in a unique habitat for angio
sperms: attached to rocks in river rapids and waterfalls. Little taxon
omic work has been published on New World Podostemaceae since Van Roye
n's monograph in the early 1950s. A paucity of complete herbarium mate
rial severely limits taxonomic study and precludes addressing a range
of enigmatic ecological and evolutionary issues that relate to the fam
ily. The size, high level of endemism, and life history of the family
are discussed. The distributions of two species in Mexico are used to
illustrate the need for concerted collecting efforts. Recommendations
for collection strategies are made that reflect the unusual habitat an
d life history of these plants.