Racomitrium spec.

cell network of Racomitrium aquaticum

Cell network of Racomitrium aquaticum with the thickened cell walls.

Family: Grimmiaceae(de); Order: Grimmiales(de)

Under the microscope members of this genus are easy to recognize by the cell walls, which are knotty thickened similar to barbed wire, as can be seen on the picture.

The plants are rather robust, and avoid, with a few exceptions, calciferous places. They are decumbent or erect, and form loose cushions. The robust principal stems wear short shouts. The leaves are in most cases lanceolate, sometimes lingulate. Frequently they end with a hyline hair.

In total the genus consists of about 80 species. In Europe -depending on the view- about 10 species can be found.

The picture on the right shows the cell network of Racomitrium aquaticum (P.Beauv.)Brid. This species grows on humid rock. Its leaves are lanceolate. The tip is rounded and a bit irregularly serrate. The species can be found worldwide in colder regions - in Europe mainly in the mountains.

Racomitrium aciculare (Hedw.) Brid.

This Racomitrium species is rather easy to recognize: Its leave don't have a glass hair, but are broadly and obtusely rounded, with some irregular teeth. The cells in the upper part of the leaf are round or short rectangular, but not elongated. The midrib ends in the tip of the leaf.

The species forms dark green or blackish cushions on chalkfree stone (preferably primary rock) in or near brooks. It can be found in whole Europe, in North America and in the Near East. In central Europe it isn't very rare.

leaf of Racomitrium aciculare

Leaf of a Racomitrium aciculare from the Thorsmørk on Iceland.

Racomitrium fasciculare (Hedw.) Brid.

The species too is easy to recognize by the form of the leaves: They are long and narrowly acuminated. There is no glass hair. The the cells in the upper part of the leaf are much longer than broad.

The short shouts at the side of the principla stems, which can be found in all Racomitrium species, are particularly numerous in this species.

The species can be found scatterd in all regions of moderated or cooler climates of the north hemisphere. It grows preferably on chalkfree stone, where it forms yellowish or brownish green cushions. In central Europe it is found mostly in the mountains. But it is nowhere frequent.

leaf of Racomitrium fasciculare

Leaf of a Racomitrium fasciculare from the Thorsmørk on Iceland.

by Michael Becker, 8/2000. Translated: 4/2002:
Last modification: 2/2002.