Family BRACHYTHECIACEAE

Microhabitat

This moss is generally found on trees (poplar, maple, oak, horse chestnut, Douglas-fir, western redcedar) as well as on rocks (cliffs), frequently in a vertical position. It is found in shaded to open areas, and from sea level to 1600 m in elevation. Our specimen came from a hardwood tree right at the end of Tatlow trail next to the ocean.

Distribution

Homalothecium nuttallii is found in North America in regions bordering the Pacific Ocean from Alaska south to California.

Typical microhabitat
Photo Credit: Yan Zhuang

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Morphology

The small to medium sized plants grow in fairly tight mats to loose strands, and are yellow to yellow-green in colour. In this dioicous species, male plants are the same size as female plants or dwarf. The stems are densely pinnately branched. The leaves are 0.7-2.1 x 0.2-0.6 mm, with a costa extending 55-82 % of the length of the leaf. The capsule is erect, curved, and 2.0-2.8 x 0.5-0.6 mm. The seta is 0.7-2 cm long. Its capsules mature in the spring.

Key identifying features

There are several other species of Homalothecium in B.C. Homalothecium nuttallii can be distinguished from H. aureum by having erect as opposed to inclined capsules, by the presence of teeth on the leaf margins (lacking in all other Homalothecium species) and by its epiphytic microhabitat (H. aureum is frequently on rocks and in grass). Homalothecium nevadense grows only on rocks in the interior of the province. Other species found in B.C. are H. arenarium and H. lutescens.

Interesting notes

The genus name means ‘straight capsule,’ but this species has a curved capsule! The species is named after famed 19th century North American botanist, T. Nuttall. A recent study of the genus divides Homalothecium into eight species found in four broad regions of the world: western North America, Newfoundland, Europe and the Mediterranean, and East Asia into Oceania. It has also been included in several studies of the family Brachytheciaceae where it has been found to be a natural and monophyletic genus.

Selected References

Hofmann, H. 1998. A monograph of the genus Homalothecium (Brachytheciaceae, Musci). Lindbergia 23: 119-159.

Huttunen, S., and Ignatov, M.S. 2004. Phylogeny of the Brachytheciaceae (Bryophyta) based on morphology and sequence level data. Cladistics 20: 151-183.

Ignatov, M.S., and Huttunen, S. 2002. Brachytheciaceae (Bryophyta) – A family of sibling genera. Arctoa 11: 245-296.

Lawton, E. 1971. Moss flora of the Pacific Northwest. The Hattori Botanical Laboratory, Ninchinan, Miyazaki, Japan.

Schofield, W.B. 1992. Some common mosses of British Columbia, 2nd ed. Royal British Columbia Museum, Victoria, Canada.

By Will Iles

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© 2006 Department of Botany, University of British Columbia