I spend my free time observing the organisms in moss, with little consideration for the moss itself. On a wet locked-down Saturday, I decided to explore that habitat of the organisms I explore in Moss Safari.
After an unusually dry April, it had rained all night and all morning, sodden moss cushions were scattered on the patio having been blown from the Eastern side of the roof. When the rain finally stopped, I went out to encourage the dogs to do their business. While they sniffed around, I selected a fallen cushion from the wet patio slabs. I was drawn to it by the fact it seemed intact and that it was of a reasonable size.
This piece was around 35mm by 35mm and a thickness of about 10mm. Its shape was reminiscent of the island Iceland: almost round, but uneven edges, like a roughly torn circle of paper (Figure 1). My identification skills of moss are limited, I like to think I can recognise a Sphagnum, beyond that I’m a novice.
I brought the moss cushion indoors and decided to attempt to identify it. I placed it under an LED magnifying glass. I took some pictures with my iphone, measurements with a ruler, and spent some time sketching features with a 2B pencil and fineline Unipens. I find sketching really helps me study something in detail that just looking alone cannot achieve.
At first the cushion looked unimpressive, just a furry, dark, greenish mass, with little stems pointing out, perhaps like an old woollen carpet. The mass itself is dark, like dirt. When I turn it over it is a matted soil colour, with rich brown strands, which I assume are the moss roots, rhizoids (Figure 2). The base is very flat, looking like it has grown against the surface of the roof tile. It is likely to have dislodged in the wind and rain, or maybe one of the pigeons that survey my garden from the roof, knocked it off in one of their amorous scuffles. Trapped amongst the matted base is some round white grit (less than 1mm) and what looks like a very small woody fragment.
Returning it the right side up, through the magnifier, I look carefully at the plant itself. It could be like a pigeon’s eye view of a forest or woodland, a dense canopy of green. The majority of the green tops of moss are rounded spikes with only the hint of leaves held closely to the stem. However, there are some particularly distinct patches of what I want to call (incorrectly) florets. The leaves are spread out from the stem, their tops brownish, and protruding from the tip of each pointed leaf is a long white hair like structure.
In just one of these many hairy florets is a single much longer structure that rises above the canopy, but curls in on itself. It looked at first like a germinating seed, but on closer inspection, the structure that is reddish at the base and yellowish towards the top, has a yellow pod curling back into the canopy. It could have easily been dismissed as a piece of cotton without closer inspection (Figure 1).
To find out which moss this moss is, I need to do some research, I take to Google and type in ‘roof moss uk’, which throws up hundreds of hits for roof moss removal: people clearly don’t like moss on their roof. So instead I try ‘roof moss identification.’ This gives me a particularly useful link, The British Bryological Society.
Moss identification is not as simple as you might expect. There is a whole range of specialist language for moss anatomy and identification usually relies on at least a hand lens and sometimes even a microscope to observe the cross-section of leaves. However, I managed to get my search down to four mosses that form cushions (acrocarp growth form) on rock and are present in lowlands: Tortula muralis, Grimmia pulvinata, Schistidium crassipilum and Orthotrichum anomalum.
An article by Sharon Pilkington was helpful in doing this and with a bit of further reading, looking up pictures online and being distracted by other interesting articles, I settled back upon this The British Bryological Society field guide.
I have come to the conclusion that the moss cushion I have been studying is Grimmia pulvinata, also known as Grey-cushioned grimmia or, my preference, ‘Hedgehog Moss.’ Those ‘hairs’ on the leaves are a give away, apparently:
From my observations of the moss cushion, these features match the field guide descriptions:
forms round, almost furry, grey cushions about 1–2 cm tall – in part
narrow leaves are 3–4 mm long, nerved to the tip, with recurved margins – yes, after I’d looked up ‘nerved’ (the central vessel through the leaf) and ‘recurved margins’ (folded).
important character is the leaf tip, which is abruptly contracted into a long hair point, which may be almost as long as the leaf blade – yes in some places
Oval capsules usually abound, bending back into the cushion on an arching seta – although only one example, this is very apparent – the ‘seta’ being the stalk on which the capsule (pod) sits.
In moist conditions, cushions appear dark green, the densely arranged leaves spread away from the stem and the hair points are only moderately conspicuous. When dry, the leaves fold together, with the result that the long, silvery hair points loosely entwine. This is a wet sample and it is dark green, densely arranged, with only some
How confident am I with my identification? It’s hard to say. I am aware of how much I don’t know. The growth form, location and leaf hairs seem to be a strongly matching. I can’t help that notice that the moss cushion is very variable. Maybe I have more than one species in the cushion, maybe it is not fully matured, maybe some of it is damaged or diseased. Time and experience will tell.
I am studying this moss cushion knowing that within this mass is an ecosystem of microscopic organisms. Between these moss stems, moss leaves and moss roots will likely be wriggly nematodes searching out bacteria and fungi to eat amongst the matted rhizoids, tardigrades lumbering around having recently emerged from their ‘sleeping’ state perhaps looking around for a piece of algae to eat, rotifers may be attached to a stem, stretched out in a pocket of water, with their cilia causing a tornado current as their jaws grind the debris dragged into them, and a testate amoeba may have extended their pseudopods like octopus tentacles to creep along a stem or leaf engulfing microscopic plants and animals that happen to be in their way.
I have got a lot more to learn about the species of moss that live on my roof and their adaptations to the environment in which they grow. In turn this will help me understand the ecology of the organisms that live in this incredible habitat.
Moss Safari 