Orthotrichum Moss

Description

Orthotrichum rupestre, The strongly hairy, reddish calyptra is the most striking feature of this north-western species. Its loosely branched tufts are 1-4 cm tall, and often rather reddish-brown as well, although they may be dull, dark green. Leaves are 3.5-4 mm long, and capsules are about 3 mm long. Like most Orthotrichum species, capsules are produced abundantly, ripening in the summer. They have 8 united pairs of peristome teeth that are erect when dry. Unlike most Orthotrichum species, the dry capsules of O. rupestre are only slightly furrowed when dry. The strongly hairy calyptrae distinguishes O. rupestre from other mosses growing on rock, such as O. anomalum (p. 656) and O. cupulatum (p. 657), both of which have sparsely hairy calyptra. Capsules that have shed their lid can also be distinguished by having 8 rather than 16 peristome teeth, and by being scarcely furrowed when dry. Capsules of O. striatum (p. 646) that have shed their lid are smooth with 16 reflexed peristome teeth, and O. striatum is almost entirely restricted to trees. In much of Scotland, this moss is a frequent feature of exposed boulders, especially igneous ones, particularly by lochs and rivers. Further south it has been noted on sarsen stones and orchard trees, but it is much less common on trees and shrubs in Britain than it is in the Mediterranean.