There are 13 species of Fissidens known or expected to occur in Delaware. A key to these species is given along with the following information for each species: short description; comments on ecology; distribution in Delaware; total range distribution; and citations to illustrations in selected North American floras. The two most credible theories for the origin of the odd Fissidens leaf—enation vs. axis reorientation—are noted. Evidence is given in support of the theory that this odd leaf morphology is due to the reorientation of the mitotic spindle of the leaf apical cells. A possible cause for this reorientation—the similarity between the two-sided stem apical cell and the two-sided leaf apical cells—may have resulted in the formation of a leaf lamina in the plane of the apical cell of the stem. As a result the entire stem can be envisioned as though it were a single leaf. Important morphological features of Fissidens are described and particular attention given to the variations exhibited by unequal vaginant laminae.

Pylaisia selwynii Kindb., which is distributed in Asia and North America, is synonymized under the older combination, P. condensata (Mitt.) A. Jaeger, based on a morphological investigation of the type material.

The publication of A Catalog and Atlas of the Mosses of Ohio (Snider and Andreas 1996), and the formation of the Ohio Moss and Lichen Association in 2004, have led to a renewed interest in Ohio bryophytes, and to significant additions to the knowledge of Ohio mosses. Since 1996, from collections made on annual forays, independent field trips, and annotations of existing herbarium specimens, 17 species have been added to the list of Ohio mosses. Snider and Andreas (1996) listed 12 species cited in literature without locality data. County distributions, either from field collections or herbarium specimens, have been located for five of the twelve species. Fourteen species, whose county distributions were reported from literature citations (Snider and Andreas (1996), have been verified with existing herbarium specimens or new collections. Ten species listed in Snider and Andreas (1996) have been excluded from the Ohio moss list.

Sphagnum compactum DC is rare in southern Illinois with five known locations some 400 km south of sites in northern Illinois. We examined habitat preferences of this species in southern Illinois, where it occurs exclusively on shaded, north-facing sandstone cliff faces and canyons, all just south of the maximum extent of Illinoian glaciation. We consider these populations to be long-lived and perhaps represent isolated relict occurrences of the species. We also report Sphagnum henryense Warnst. new to the area.