This is a ‘microscope only’ moss, which is indistinguishable from B. capillare in the field, with the same corkscrew arrangement of the dry leaves and the same leaf shape. Habitat is the key. Remember – when you see such a plant growing on free-draining calcareous soil, such as the sides of anthills in chalk grassland, take home some fruiting material.
Under the stereomicroscope, remove a fruiting plant, peel away the perichaetial leaves and look at the sex organs clustered around the base. If the inflorescence is synoicous, it is B. torquescens. A confirmatory character is that the apical cell of the paraphysis is pointed not rounded as in B. capillare.
Pretty straightforward…? Well, OK if you are familiar with the details of moss sexuality, but maybe a brief tutorialette would be helpful at this stage.
You need to familiarize yourself with the difference between antheridia (the male sex organs) and archegonia (the female organs) in Bryum species. Collect some fruiting B. capillare from your garden or a nearby wall-top. This species is dioicous, so any plants with capsules will have only archegonia at the seta base. Under the microscope they look like long, thin vases, with a well-defined neck, and a slight swelling at the base (the venter) which often contains an egg, appearing as a dark smudge. You may need to root around a bit for separate clusters of male plants of B. capillare, probably elsewhere on the wall, but persist and you will eventually find them somewhere, without capsules, of course, but with curious swollen shoot tips, filled with tiny roundish structures, like mini birds’ nests, stuffed with eggs. These latter are antheridia, the male organs, looking under the microscope like little Zeppelin airships, but with longitudinal and transverse cell walls visible, arranged in regular rows and columns.
Now you have familiarized yourself with these structures, you have moved up a notch in your bryoskills – determining sexuality is a very useful tool for bryophyte identification. It seems a bit overwhelming to start with, but have a few ‘goes’ at material of common stuff which you know and whose sexuality you can look up, until you get the hang of it. Soon your heart will no longer sink when you read ‘inflorescence synoicous’ or the like and you will cheerily set to work hunting for inflorescences and the extra information they give you. You are now all set to look at your undetermined specimen to see whether it is synoicous or not.
You need to be aware of a couple of complications. Firstly, the archegonia, when in good condition, look very different in shape from antheridia as they have the long thin neck at the top, lacking in the antheridia. However, these necks can break off, leaving a structure which can resemble an antheridium and mislead the unwary. Check that your ‘antheridium’ has rectangular cells arranged in regular rows and columns as referred to above, like a tiled floor. The cells in the lower part of the archegonia (the venter) are usually more quadrate, less distinct and more irregular in size and arrangement in many species. This helps you to tell apart an archegonium which has lost its neck, from a real antheridium. Secondly, as the inflorescences age, the antheridia decay first, leaving only archegonia in older inflorescences, leading to the false impression of a female only inflorescence. Always look at several shoots when trying to determine sexuality and beware of old, tatty ones. Remember too that while you can be sure a plant is synoicous or autoicous, having found antheridia and archegonia, you can never be absolutely certain it’s dioicous, as antheridia might have aged and fallen away, or you may not have found the male branches. Search carefully on several shoots. There are some useful drawings on p14 of David Holyoak’s book, ‘European Bryaceae’ and lots of helpful detail.
Do have a go at recording this one – it is not that uncommon, but rarely recorded, as many bryologists shy away from poking about in inflorescences. Not you though.