Ceratodon Bridel, 1826.

Ceratodon is especially easy to recognize from the strumose and sulcate, lightly curved capsule.

Key to Ceratodon

Here we include a single genus that has lanceolate leaves with margins recurved to near the apex and has quadrate, smooth cells tending to be arranged in longitudinal rows. One should here note the almost straight (no acumination) margins of the leaves and the remote serrulation near the apex. The dry leaves vary from very crispate to almost not at all.

Species included in this key are in Ditrichaceae:
Ceratodon purpureus (Hedwig) Bridel
Ceratodon stenocarpus Bruch & W. P. Schimper

Ceratodon is one of the most widespread weedy mosses in the world, being found on every continent including Antarctica. It is especially confusing because the ovate-lanceolate to lanceolate leaves with recurved margins signal Didymodon. This confusion is compounded by the several ecological and morphological expressions of C. purpureus. Even seasoned bryologists sometimes discover that a puzzling specimen is simply this weedy plant. The smooth cells of Ceratodon may not be the aid in identification that one might wish because Didymodon may have papillosity so low as to be ignored without careful observation. Our two species of Ceratodon have similar gametophytes, and these gametophytes have a special pattern of remote serrulation near the apex (best seen in leaves from distal portions of the stems). Observation of such a pattern of serrulations is sufficient to signal the identification. The two species are distinguishable by seta color only when the sporophytes are fully mature. Ceratodon is generally abundant along road banks and other disturbed sites.

A. Seta yellow; plant occasionally locally introduced .....Ceratodon stenocarpus
A. Seta red-brown; plant widespread, especially in disturbed sites .....Ceratodon purpureus