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:
- 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:
- 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.
- Once the plant is in a good position, fold over the other page of the double page spread.
- Add some more sheets of newspaper to the top and bottom of the folded newspaper with the specimen inside.
- Put the newspaper on a hard, flat surface.
- Place a few heavy books on top of the newspaper.
- 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.
- 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!
- 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.
- 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.
- 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:
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.