Tortula acaulon (Withering) Zander, also known as Phascum cuspidatum Hedwig
Tortula acaulon is a very small (2-4 mm), ephemeral moss, which grows on exposed soil, often in disturbed areas, in dense clusters or scattered amongst other small and ephemeral moss species. Here in Santa Barbara County, the leaves typically have long awns, which give the clump a furry appearance. The very short sporophyte is immersed within the leaves, which envelop it rather loosely, and its shiny brown oblong capsule is easily seen when it matures.
Scroll down for more photos (click to enlarge) and descriptions of habitat, plants, leaves, sporophytes, spores, distribution map, name origin, and similar species.
Habitat: Tortula acaulon grows on seasonally moist soil, often in disturbed areas, in partial shade or full sun.
Habit: Tortula acaulon plants may form dense clumps or be scattered amongst other ephemeral moss species.
Plants: Tortula acaulon plants are budlike, with just a few leaves originating from a stumpy stem. When moist, the leaves are held slightly outward, revealing the sporophyte capsule. When dry, leaves become more erect and overlap one another, loosely enveloping the sporophyte.
Leaves: Tortula acaulon leaves are oblong, of various sizes, with inner leaves longest (to 3.5 mm) and outer leaves shortest. Leaves may or may not have a long awn, though all plants I have encountered here in Santa Barbara County have had at least some leaves with very long awns, particularly the large innermost leaves which surround the sporophyte (perichaetial leaves). Margins of longer leaves are recurved.
Sporophytes: Tortula acaulon sporophytes are very short (1-1.5 mm), and are immersed within the leaves, but not fully hidden. Capsules are spherical to oblong, becoming shiny chestnut brown when mature, and have a pointy cap (calyptra) which covers the variable nipple-like apiculus on top. The stalk (seta) is very short and unless dissected out, the sporophytes appear to be sessile. Upon maturation, the capsule simply decays (is cleistocarpous) to release the brown, finely papillose spores.
Distribution: Tortula acaulon is found throughout North America and Europe, as well as in Asia, Africa and New Zealand.
Similar Species in Santa Barbara County
Acaulon muticum var. rufescens, another ephemeral moss growing in similar habitat, is smaller and more budlike, with leaves which lack awns and overlap tightly, completely obscuring the sporophyte. See photo below with the two species side by side.
Stegonia hyalinotricha, another ephemeral moss growing in similar habitat with very long hyaline awns, is smaller and more budlike, resembling miniature onions, with leaves tightly overlapping and completely obscuring the sporophyte.
Ephemerum serratum, yet another ephemeral moss growing in similar habitat, is much tinier, and likely to be overlooked, but may be collected along with other mosses, including Tortula acaulon. See photo below with the two species side by side.
Bryophytes of Santa Barbara 