Bryology is the study of the plant order Bryophyta, (Philips, 1980) which contains the sub-classes of Mosses (Musci), Liverworts (Hepaticae) and Hornworts (Anthocerotophyta).
In taxonomic classification terms these simple plants are contained within the sub-Phylum of bryophytes and are the ancestors of the first land plants on earth. Bryophytes were the first land plants to emerge (during the Silurian period) around 460 million years ago (Anon, 1996) from the single-celled aquatic eukaryiotic organisms contained within what was known as the ‘Primordial Soup’ (Anon, 1996).
The main differences between bryophytes and the more complicated plants that evolved from them (such as trees and flowers) is that:
1) Bryophytes reproduce via spore dispersal instead of developing seeds and;
2) Bryophytes do not have any roots but instead have rudimentary root-like structures called rhizoids.
3) Mosses, liverworts and hornworts are classified as nonvascular land plants meaning that they do not possess vascular tissue known as xylem. A xylem is made up of a cellular compound known as Lignin, and allows trees etc to uptake water via translocation. The lignin contained within a xylem results in the coarse tissue that makes trees woody; its absence in bryophytes means they are exclusively comprised of soft plant tissue.
Bryophyte classification
Geographical location and Habitat
There are thought to be around 15, 000 species of bryophytes, containing around 9,000 species of moss and around 6,000 species of liverworts and hornworts (Anon, 2009).
As Bryophytes themselves lack the necessary structures to uptake water, they are often found in damp conditions whereby they can absorb water through osmosis (Philips, 1980). As a result various mosses such as Bryum cryophyllum (found in the Northwest region of Canada) occur ubiquitously on rocks along rivers and lakes (Anon, 2009).
Mosses and Liverworts are found anywhere in the world where there is water, except in the sea itself. They can be found in streams, rivers, along lakeshores and even in deserts, and can even be sustained from inter-tidal sea spray; examples have even been found in Antarctica (Anon, 2009b).
Reproduction in Bryophytes
During reproduction water is vital to bryophytes as it facilitates the dispersal of spermatozoa’s, or the reproductive cells of mosses and liverworts. For example, moss species reproduce via the dispersal of microscopic spores that land on a damp surface and then germinate (Anon, 2009b). Mosses may forcibly eject spores through a small opening (known as a sphagnum); release them through four slits (Andraea), or as in the majority of moss species, through an opening when the lid of the fruit stalk (Phillips, 1980).
Liverworts
Liverworts are either flat-lobed structures, which may superficially resemble succulent vascular species such as some cacti species, or have small leaves in rows of three. The means of reproduction is different to mosses in that capsules break open into four flaps, releasing the spores (Phillips, 1980).
What you need to be a Bryologist
Bryology is a specialist scientific study and requires certain equipment as well as an intimate knowledge and understanding of bryophyte anatomy, to identify the seemingly identical 9,000 species of moss and 6,000 species of liverworts.
Equipment
Although a good knowledge of bryophyte identification is needed to be a professional bryologist, basic equipment can allow anyone to enjoy the diverse world of bryology.
Some equipment you will need includes:
A hand lens is essential in identifying the characteristic spore heads that distinguish moss species from each other. A X10 lens is useful for general studying but a X20 will be needed for fine detail (Anon, 2009c).
A identification guide is also crucial in studying bryophytes to compare the characteristics of the plant you have in front of you with the key in the book. The keys work by choosing bryophytes with similar structures and characteristics to the plant in front of you, ruling out incorrect species via a process of elimination until you arrive at a species that roughly resembles your specimen (Anon, 2009c).
A microscope will often be the only way of determining the species of some bryophytes, as the determining features such as spore heads, are virtually invisible to the naked eye. A high power compound microscope in the range of X40 to X400 will be needed to identify most small moss species (Anon, 2009c)
What use is the study of Bryology in the real world?
Liverworts and lichens are biological indicators of clean air and only grow in abundance in areas with extremely pure air. For example the dense forests of the Pacific Northwest of America, particularly in Oregon are saturated with lichens and liverworts, and the air in the region is extremely clean. So in this way bryologists and other scientists can gain an immediate visual indication of the air quality in a given area. If bryophytes are absent from an area it may indicate poor air quality and therefore other environmental issues.
References
Anonymous. (1996). Oxford Dictionary of Biology. Oxford University Press.
Anonymous. (2009). “What is Bryology?” From http://www.bryology.org/bryodesc.html (Accessed 10/07/09).
Anonymous. (2009b). “What is a Bryophyte?” From the British Bryological Society http://rbg-web2.rbge.org.uk/bbs/Learning/whatis.htm (Accessed 10/07/09).
Anonymous. (2009c). “Getting started in bryology”. From the British Bryological Society http://rbg- web2.rbge.org.uk/bbs/Learning/getting_started.htm (Accessed 10/07/09).
Phillips, R. (1980). Grasses, Ferns, Mosses and Lichens of Great Britain and Ireland. Macmillan, London.
