Dichelyma Myrin, 1833.

The one California species of Dichelyma has long, almost subulate, and falcate-secund leaves. Unlike other members of the primarily aquatic Fontinalaceae, it grows largely epiphytically on only occasionally submerged substrates. It may be so sparingly branched as to be confused with such acrocarpous, falcate and subulate leaved plants as Dicranum. When sporophytes are present, one will see doubly peristomate capsules with a trellis-like endostome. The sporophytes are barely emergent from greatly elongated sheathing perichaetial leaves. When capsules are absent, the lack of differentiated alar cells and the rather flat costa eliminate from consideration any Dicranaceae and immediately identify the plant.

Key to Dichelyma

Species included in this key are all in Fontinalaceae:
Dichelyma falcatum (Hedwig) Myrin, not known from CA
Dichelyma uncinatum Mitten

The two western North American species of Dichelyma differ somewhat in habitat. Dichelyma uncinatum has been found only once in California. Originally collected by Dr. Ruprecht Düll on a short trip from his German home, it grows in large quantity on the stems of Toxicodendron in a frequently flooded Acer macrophyllum forest near Willits (Mendocino County, California). This habitat reflects its pattern of occurrence in Oregon and Washington. Dichelyma falcatum is more frequently found on rocks along slowly flowing streams in Washington State. Its broader leaves may suggest Drepanocladus sensu lato but the tristichous nature of those leaves should allow easy identification.

A. Leaves linear lanceolate, mostly about 10:1, keeled but not strongly conduplicate with the tristichous character thus somewhat obscure; all leaves with costa long excurrent .....Dichelyma uncinatum
A. Leaves lanceolate, 4-6:1, so keeled and conduplicate as to appear clearly tristichous; costa on at least some leaves in a clone percurrent to very shortly excurrent .....Dichelyma falcatum not known from CA