Plants 0.2--2.5 cm, unbranched or sparsely and irregularly pinnate. Stem leaves in basal stipe region broad ovate-triangular, often very small for a large proportion of the stipe, 0.5 X 0.3 mm; distal leaves erect from clasping base, ovate-lanceolate, 1.8 X 0.9 mm; base decurrent, not rounded or auriculate; apex broadly acuminate; costa percurrent in distal leaves, medial lamina cells sinuose, 16--46 X 2.5 µm; alar cells in 7--14 rows of 2--23 quadrate or short rectangular cells 9--16 X 3--9 µm, running into decurrent wing and up leaf margin. Branch leaves in five distinct spiralling rows; ovate-acuminate, 1.1--1.7 X 0.3--0.6 mm, strongly concave with short broad flat acuminate apex; medial laminal cells 16--46 X 2.5 µm, strongly prorate, tips of prorae with low conical papillae. [Seta 5--9 mm. Capsule cylindrical, 1.8--2.7 X 0.9 mm. Calyptra cucullate, covering capsules at maturity, with scattered biseriate hairs. Spores spherical or ovoid, 30--41 X 28--35 µm.]

Sporophytes not known from flora area. Dry evergreen forest, lowland deciduous forest and hammocks, occasionally flooded palm woodland, and disturbed woodlands, on trees and tree roots, bushes, decaying wood, limestone and sandstone; 0--700 m; Fla.; s Mexico, West Indies, Central America, South America (to offshore islands in s Brazil.)

Plants of P. cymbifolia are usually small and scarcely branched, although well-grown plants (for example in the Florida Keys) may be larger and irregularly pinnate. The leaf bases are decurrent, with several rows of quadrate alar cells extending up the margin. P. cymbifolia is restricted to southern Florida. Superficially, Pireella cymbifolium may resemble Henicodium, but under the microscope the more extensive area of oblate cells in the leaf base and the distinctly plicate leaves in the latter species should prevent confusion.