Bryum argenteum is one of the most cosmopolitan mosses found throughout South Africa. It is most easily recognized by its whitish or silvery green leaves. It is widespread in driveways, on sidewalks and in back yards.

Description
Bryum argenteum is a bryophyte (moss) that forms very close tufts or cushions; it occurs in patches or is found as scattered individuals mixed with other mosses. Plants are small to medium - sized, 1 - 25 mm long. The stems are julaceous (smoothly cylindrical, like a catkin), 1-25 mm tall, yellowish green or red to red-brown, and branched below. The leaves are crowded and tightly held to the stem, overlapping each other, broadly ovate and concave and green below. The upper surface is hyaline (transparent), usually with a tapering, short point. The sporophytes consist of yellow to reddish brown, short, arched setae, 7-20 mm long and red-brown capsules, 1 - 2 mm long, drooping and wrinkled when dry. The spores are 10 - 15 µm in diameter and finely papillose. The plant is perennial.

Conservation status
None.

Distribution and habitat
The silver moss is one of the most cosmopolitan mosses, found throughout South Africa. It is commonly found in human settlements. It is prevalent in atmospherically polluted areas e.g. in big cities on tarred roads, on concrete structures (e.g. between paving stones, at the bases of walls, on roofs and windowsills), on soil as well as in waste areas.

Derivation of name and historical aspects
The species epithet argenteum refers to the characteristic silvery colour of the plant. The genus Bryum is the largest genus of the family Bryaceae. In sub-Saharan Africa it consists of about 93 species.

Ecology
Tan & Pócs (2000) mention Bryum argenteum among the mosses that have adapted to, and are more dominant in man-made habitats than in their natural habitat.

Uses and cultural aspects
No uses have been documented for Bryum argenteum in South Africa. However, overseas it is reported to be of value in pollution monitoring and control. This is due to its ability to tolerate drought and pollution of urban environments. It is also frequently used for experimental approaches to evolutionary processes.

Growing Bryum argenteum

Although it seems to grow widely, it is not cultivated and it is reported to have failed in flower pots of soil (Fletcher 1991).

References and further reading

• Fletcher, M. 1991. Moss grower's handbook : 31. Seventy Press, Berkshire.
• Magill, R.E. 1987. Bryophyta. Flora of southern Africa, part 1, fasc. 2: 361 - 366.
• Richardson, D.H.S. 1981. The biology of mosses : 152. Blackwell Scientific Publications, Oxford.
• Tan, B.C. & Pócs, T. 2000. Biogeography and conservation of bryophytes. In A. Jonathan Shaw & B. Goffinet, Bryophyte biology : 405. Cambridge University Press, United Kingdom.