Tricky Zygodons! Or are they?

Last Sunday I was able to attend a field trip of the South-East branch of the British Bryological Society, to Duddleswell Valley nestled in the expanse of Ashdown Forest. The key site in this valley is a wooded ghyll, which has been a very popular location for bryologists since at least when the brilliant botanist Francis Rose visited in the mid-1950s.

Once we had waded our way through no less than eight different species of Sphagnum mosses we arrived at this famous ghyll and what greeted us was a steep and slippery slope down to the stream below us. Luckily we all made it down safely and we were able to begin!

We worked our way slowly down the ghyll, finding extreme rarities such as Campylostelium saxicola; admiring huge walls of fruiting Pellia epiphylla and finding ourselves knee-deep in shallow-looking mud. I even managed to put my foot in the middle of the largest colony of Nardia compressa in South-East England!

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A large part of the only colony of Nardia compressa in the South-East

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Nardia compressa

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Campylostelium saxicola

Near the end of our excellent and bryophyte-rich walk we came across a good stand of willow trees with many species that we hadn’t yet encountered that day. These species included a small, inconspicuous tuft of moss, a Zygodon species. There are four regularly occurring Zygodon species in the South-East and they are hard to separate in the field. To be certain of an identification to species level you really need to get out the microscope.

Therefore I took a small part of the moss back with me to work on. I was expecting it to be a tricky task that might take me a while to perfect. What surprised me was that it was quite the opposite!

The features to look at are the gemmae. The gemmae of Zygodons are single cells that detach from the moss in order to reproduce asexually, meaning that the fusion of male and female sex-cells (gametes) is not necessary. When mosses and other organisms reproduce asexually like this it is referred to as fragmentation.

Not knowing how to get the gemmae off the moss and onto the microscope slide to examine, I first tried taking a small stem of the moss and seeing if I could spot any gemmae around it. This was unsuccessful and so for my second attempt I simply tapped the clump of moss onto the slide, added a drop of water and a cover slip. I placed this slide under the microscope and I could immediately see several gemmae under 100x and 400x magnification. That was much easier than I had expected!

Next came the actual identification of the Zygodon. The very helpful Brad Scott had narrowed my moss down to two species, Z. conoideus and Z. viridissimus. He also supplied photos of the gemmae of both conoideus and viridissimus, so all I needed to do was compare the gemmae of my moss with Brad’s excellent photos. It was clear: my moss was definitely Zygodon conoideus!

This experience has certainly shown me that not everything that needs microscopic examination is difficult. Certainly some species require very fiddly work to separate but that is not always the case.

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My photo of a gemma of Zygodon conoideus

Starting a Herbarium

For centuries botanists have been collecting specimens of the plants they observe. If done correctly, botanical specimens can last for a very long time. For example, the Angela Marmont Centre at the Natural History Museum has specimens collected by Charles Darwin and Alfred Russel Wallace. Specimens can be very useful in documenting regional variation and how a species has changed over time.

Last weekend I was out with the South-east branch of the British Bryological Society recording mosses and liverworts at Devil’s Dyke, north of Brighton. As is often the case, however, one of the highlights of this field trip was in fact not to do with the subject of our search! Once we had passed through a section of Ash woodland on our walk we came to a lovely crystal-clear chalk pond. Despite few bryophytes around the pond’s edges the pond was full of life, including several water plants. Most common was the Ivy-leaved Duckweed, Lemna trisulca, and there were also a few Potamogeton natans plants as well. However what really caught our eye was a very beautiful looking pondweed with a lovely texture and colour that was unfamiliar to me but not for the other members. They identified the pondweed as Groenlandia densa, otherwise known as the Opposite-leaved Pondweed.

Groenlandia densa is not a very common species and is sadly declining in Britain. This is mostly due to urbanisation, and therefore it is missing from the vast majority of London. It has also declined due to a factor known as eutrophication which is the presence of excessive nutrients in a water body. This is most commonly caused by run-off from the nearby land, and it creates a dense growth of plant life which can potentially displace species that cannot compete. Due to this decline, it was suggested that I collect a piece of the pondweed, in case it becomes a very rare species and little material for herbariums could be found without damaging a population.

It is easy for anyone to start preparing plant specimens; little specialist equipment is needed. This is all that is needed for a beginner to make a good quality specimen:

  • newspaper
  • heavy books
  • a dry environment
  • good quality card
  • PVA glue
  • printed labels

And these are the steps I went through to create my pondweed specimen:

  1. Lay out the specimen on half of a full double page spread of newspaper in a way that should show as many features as possible.
  2. Once the plant is in a good position, fold over the other page of the double page spread.
  3. Add some more sheets of newspaper to the top and bottom of the folded newspaper with the specimen inside.
  4. Put the newspaper on a hard, flat surface.
  5. Place a few heavy books on top of the newspaper.
  6. Leave the specimen until it is sufficiently dry and flat, this could take a few weeks or only a few days, but don’t overdo it and don’t leave it for too short a period.
  7. Once the specimen is ready carefully take it out from the newspaper and lay it out on your piece of card making sure that it shows the necessary features. Remember to leave room for a label!
  8. Using PVA glue or any other glue recommended by botanists, stick the specimen down on the card. PVA glue dries clear so don’t worry too much if you get some on the card where you don’t want it.
  9. Fill in a label. Ideally the label should show as much information about the plant as possible: species; family; collection number; locality (grid reference, name of site, nearest town, county etc.); habitat; collector’s name; date of collection; and also note down features of the plant that may have been lost in the drying process.
  10. Finally, and optionally, you could also attach a small paper envelope to the specimen containing dried fruit/seeds that would have been ruined in the pressing process.

And there you have your specimen! This is what my pondweed looked like before and after collecting, pressing and mounting:

This is not the only specimen I have so far collected. At the beginning of the summer, as part of my interest to record the slightly trickier-to-identify species, I collected a couple of Bramble (Rubus) species. These were the first specimens I collected and I was quite pleased with the result. However, they weren’t good enough. After I had dropped them off at the Angela Marmont Centre at the Natural History Museum, Dr David Allen kindly looked at them for me. Unfortunately they were lacking some necessary features vital in identification, such as a section of the first year growth. Using his advice, I went out recently and collected a specimen of a particularly late-flowering Bramble, and this was the result:

bramblespecimen

I will also attach with the specimen a couple of photos of the plant before it was collected:

This shall hopefully even further aid identification and maybe contribute to the understanding of this poorly known group.

Many groups are overlooked, because they are tricky to identify or they are too small or they need specialist equipment to collect. Some examples are dandelions, a nightmare of identification; desmids, microscopic algae; and parasitic wasps, also very difficult to identify. This results in these groups being little-known as few people are willing to try to find and identify them. This leads to under recording of species that are probably common, creating deceptive data. One of my aims is to try and master these very difficult groups and hopefully make a difference.

Introduction to Bryophytes

Bryophytes are mosses, liverworts and hornworts, and they are an amazing part of natural history. However, many people don’t know that, so this is why you should become interested in Bryophytes:

  • They are rather unrecorded. It is so easy  just to note the bryophytes you see on a short walk that it is hard to believe how few people actually do it. With a better understanding of them, they will be easier to conserve.
  • They can be found nearly anywhere! On trees, walls, houses, all over the place, even one or two on cars and underwater!
  • There are so many species! There are only 4 species of Hornwort, but you can find 763 species of mosses in the UK and nearly 300 Liverworts. Bryophytes love wet climates so that’s why Britain has about two-thirds of all European species!
  • Unlike some species which can only be studied some parts of the year, Bryophytes can be studied year-round. It is probably even easier to find Bryophytes in winter as they are much less likely to be covered by large plants!

I’ve only found 32 species so far and some can be quite difficult to ID, especially Sphagnums (bog mosses), therefore I recommend buying the British Bryological Society’s Field Guide for UK and Ireland. It can help you identify most of the species you find and has been put together by ‘a team of expert bryologists’. It includes keys, photographs, similar species, colour coding, drawings of key features etc.

It is easy to get started with finding Bryophytes, there isn’t too much equipment involved. The only thing beginners really need is a good hand lens but don’t worry if you don’t have that just yet, many species can be easily identified with the naked eye. I would suggest starting in your own garden, big or small, as there is bound to be many easy species there and is a good way to practise. But most of all: enjoy it!

Dotted Thyme-moss

Dotted Thyme-moss

Urn Haircap, my 32nd species

Urn Haircap, my 32nd species