Jonathan Sleath gave a presentation entitled The Hidden World of Mosses and Liverworts on 21st November for the Friends of the University of Bristol Botanic Garden. He described bryophytes as his sideline while a GP. Retirement now allows him to pursue his hobby unfettered. The fascination started in childhood. He set out to convince an audience of garden-lovers how attractive and appealing bryophytes can be.
What’s the Attraction?
Mosses do not run away like animals. Liverworts do not fly away like birds. You can indulge your bryological interests without venturing far from home. Mosses will appear within paces of your front door. Bryology is a great winter sport. You can collect specimens and store them easily to investigate on cold, dark winter evenings. By contrast, fungi quickly turn into a disappointing liquid mush, even in the fridge.
The novice bryologist gains quick recognition as an expert. So few people know anything about mosses, liverworts and hornworts. Bryophytes offer a great excuse to play about with microscopes. The beauty and variety in their structures is fascinating. Their correct identification appeals to those who enjoy a challenge. Jonathan Sleath’s interest has brought him into contact with other moss and liverwort enthusiasts. He recommended the British Bryological Society, local meetings, publications and online communities.
UK bryophytes are rich and well-documented. The West, along with Ireland, are of international importance for oceanic bryophytes. There are approximately 1,050 species in Britain, more than half of all European species. This richness can be attributed to Britain being at the meeting point of several biogeographical zones.
Bryophytes are among the earliest known land plants. There are relatively few fossils, but DNA analysis is starting to reveal more information.
Hornworts are not that common. You need to seek out disturbed ground to find them.
Liverworts can be divided into 2 types: thallose and leafy.
Thallose liverworts have a flat ribbon of tissue like seaweed. They are thick, making it difficult for gases to pass in and out. They don’t have complicated structural mechanisms. Examples shown that can be found in the British Bryological Society’s Mosses and Liverworts of Britain and Ireland: a field guide were:
- Conocephalum conicum, Great Scented Liverwort (Marchantiales) is thick. Look closely and you see that its surfaces are covered in dots. These are air pores. It is found at the edges of streams in woods.
- Lunularia cruciata, Crescent-cup Liverwort (Marchantiales) is weedy and found in trampled, often urban areas.
- Metzgeria furcata, Forked Veilwort.
- Riccardia sp. with sporophyte (see photo below).
Leafy liverworts have a stem with rows of leaves that are often toothed or divided. They have different structures like underleaves and special adaptations to help them retain water, e.g. hairs. Some of the leafy liverworts shown were:
- Lophocola bidentata, Bifid Crestwort (Jungermanniales) has conspicuously bilobed leaves (See also French INPN website in English).
- Radula complanata, Even Scalewort (Jungermanniales) has entire leaves.
- Pleurocladula albescens, Snow Threadwort (Jungermanniales) has concave, shell-like leaves that are adapted to trap water.
Jonathan Sleath then moved on to discuss mosses. Mosses are divided into Acrocarps (upright mosses), Pleurocarps (sprawling, branches mosses) and Sphagnum (bog mosses).
We saw a number of familiar upright mosses including:
- Mnium hornum, Swan’s-neck Thyme-moss (Bryales) is a starlike, woodland moss.
- Orthotrichum pulchellum, Elegant Bristle-moss (Orthotrichales).
- Tortula muralis, Wall Screw-moss (Pottiales) found on walls as name suggests.
- Atrichum undulatum, Common Smoothcap (Polytrichales) is a woodland moss.
- Fissidens dubius, Rock Pocket-moss (Dicranales) has a flattened appearance.
We saw a few sprawling, branching mosses:
- Rhytidiadelphus squarrosus, Springy Turf-moss (Hypnales) is commonly found in garden lawns.
- Pleurozium schreberi, Red-stemmed Feather-moss (Hypnales).
Jonathan Sleath showed us slides of moss cells with chloroplasts visible under the microscope. There was considerable variation in shape: circular, angular, square, hexagonal, elongated, etc.
Sphagnum is particularly special. It enjoys waterlogged, acid conditions. It forms peat. The pores let water both in and out. It acts like a sponge. We saw the explosive mechanism of a sporophyte, structure of a sphagnum leaf and the wide variations in colour. Examples included:
- Sphagnum pulchrum, Golden Bog-moss (Sphagnales)
- Sphagnum fimbriatum, Fringed Bog-moss (Sphagnales)
- Sphagnum cuspidatum, Feathery Bog-moss (Sphagnales) is also evocatively known as the Drowned Kitten Moss for its soggy cat-like appearance.
Mosses are not generally recognised for their economic uses. Sphagnum stands out as the most famous example. It has been used since Anglo-Saxon times to treat wounds. It offers an absorbent material with faint antiseptic properties. During the Napoleonic Wars, it was systematically collected for this purpose. North American Indians used it for nappies.
The importance of preserving Sphagnum in peat bogs is now gaining increasing recognition due to the climate emergency. Sphagnum peat bogs need to be kept wet to store carbon emissions in the ground. Peat that is allowed to dry out and deteriorate will do the opposite. It will release carbon dioxide and methane into the atmosphere. The horticultural industry poses an ongoing threat to our peat bogs. It emerged at the Wells Cathedral Climate Change Conference that peat is still being cut in Somerset and the necessity of a ban was highlighted. Mere encouragement is not working. Peat is also still being cut in Lancashire and Ireland.
Peat-free Alternative for Gardeners
Jonathan Sleath encouraged all gardeners present to switch to a peat-free alternative. It requires some adjustments, but he has successfully converted to Westland New Horizon peat-free compost. It is important to check the product labelling closely in the garden centre, as they still have some products with peat content.
Under the Microscope
Jonathan Sleath showed us some fabulously detailed slides and clips of mosses and liverworts under the microscope during his presentation. My favourite clip showed spore release in real time. During the questions at the end of the session, there was advice on suitable microscopes (40-80x magnification). It is also possible to enjoy bryology with just a hand lens. Hand lenses with an LED light are particularly useful.
© Karen Netto (Andrews) 2018-19