Identification notes

Like many other mosses, the capsules of different Bryum species mature at particular times of the year, and knowing this can be helpful in making provisional field identifications. Bryum algovicum is one such; its prodigious and plump-looking capsules draw the eye between May and August, when they mature and drop their lids.

Its most reliable features are to be seen under the microscope. Slice a mature capsule with peristome teeth in good condition lengthwise, mount the halves under a coverslip and look carefully at the outer peristome teeth. If it’s B. algovicum you’ll see vertical and oblique cross-walls between the horizontal ones, especially in the lower part of the teeth (see images below). These often trap small bubbles of air, making them look characteristically mottled. The rare B. warneum also has these (not usually so many) but has ripe capsules in late autumn to early winter.

Distribution in Great Britain and Ireland

Bryum algovicum is most commonly found in coastal habitats, but it may be overlooked inland, where it grows in other well-drained basic habitats with little competing vegetation. At present only B. algovicum var. rutheanum (which has synoicous inflorescences) has been recorded in the British Isles.