Central America is a small region (three-fourths the size of Texas) with one of the most diverse moss floras of any area of the world. The mosses of Central America are not especially endemic, but rather represent an eclectic moss flora produced by the pronounced vertical relief of the region and its close physical position to three species source areas: South America, North America, and the Caribbean. In addition, many species from Africa and Southeast Asia are found in the region. Central America as here delimited is political; it includes all parts of Belize, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, and Panama.

The Moss Flora of Central America is a four-part, revisionary flora. Parts 1 and 2, published in 1994 and 2002, respectively, treated a total of 521 species. Part 3 gives keys, descriptions, and discussions for 239 moss species. In addition, for each species precise type information is provided; distribution within Central America is documented by the examination of specimens; world distribution is indicated; habitat notes based on personal field experience or taken from collection labels are provided; and a list of previously published illustrations is given. Part 3 contains numerous genera that treat all tropical American species of those genera, as well as major treatments on Lepidopilum (18 species), Thamniopsis (13 species), Pireella (11 species), and Porotrichum (11 species); it will likely prove useful for many genera throughout the Neotropics.