“Another rare thing, lingering in caves and deserted mine adits, is the shining moss, that glimmers like dim gold under darkness. Those who snatch at it and bring it to the daylight find only a little rusty earth in their hands”.
Eden Phillpotts – A Shadow Passes
If ever you are rooting around some of Dartmoor’s boulder caves you may well peer into the dark recesses and see a strange green luminescence glowing from deep within. The first time I came across this phenomenon it was as if a pair of eyes were peering back at me, initially I thought that some reptile was hiding in the small crevice. Actually, I feared it may be an adder so decided to oust the thing with my walking stick. As nothing appeared I carefully shoved my hand in found that the weird glow had transferred to my fingers but then when they came out into daylight all that was there was a mud-like stain. What I had actually found was ‘Goblin’s Gold’ (Luminous Moss) or to be precise Schistostega pennata or as it was once known Schistostega osmundacea and on reading Worth’s Dartmoor (1988, p.72) found the following:
‘The Luminous Moss, Schistostega osmundacea, is very small, its frond-like growth rarely exceeds slightly over half an inch in height, and is delicate in the extreme. In place of growing boldly in the open it seeks some cave, a rabbit hole will serve, or the wall of an ill-lit stable, some place where none but feeble light can penetrate; but from this dark background it shines with a beautiful green luminosity. It has been said that it avoids cavities which have a southern exposure, but this is incorrect, any cavity which is sufficiently deep to exclude all but feeble light serves it equally well, and one of the finest displays that I have seen was in an old potato cave at Yellowmead, Sheepstor, the entrance to which faced due south. Moisture is essential, so that buildings in which it is found must be not only dark but also damp. The luminous effect is due entirely to reflected light. The protonema of the moss develops cells with lenses which concentrate the feeble light upon the chlorophyll granules; these absorb such wave lengths as serve their purpose, reflecting back the remainder in the direction of its source. The little cells with their lenses can move to meet a varied direction of the light. I have grown the moss for several years, and have at times so moved it that the effect has been the same as that which would have been produced by moving the light source through an angle of 45°. The luminosity is then no longer apparent, but within twenty-four hours it is fully re-established”.
As with most things, nature has a fantastic way of providing survival methods and Goblin’s Gold is no exception. It has been noted that this moss cannot easily compete with other mosses and plants and so it grows where very little else can thrive; namely dark damp recesses. In addition The Bryological Society suggests that the luminous glow of Goblin’s Gold resembles that of the reflection seen in cats eyes. Interestingly enough it has been noted that the green reflective light may attract small animals such as rodents, insects and birds which then spread reproductive spores to new areas. Despite having found several rock caves which contain ‘Goblin’s Gold’ I have never managed to get a decent photograph so unfortunately I have had to ‘borrow’ one from Wikipedia;
In Devon this moss is classified as being of ‘conservation concern’ as nationally it is becoming pretty scarce so in a way it could be described as precious as ‘Goblin’s Gold’. Considering at one time there was a strong belief in piskies and goblins who dwelt in the darkest nooks and crannies of Dartmoor. This moss must have given credence to their magical abilities. Imagine finding some Goblin’s Gold glowing in the dark and then reaching to pick it up only to find a handful of ‘rusty earth’? Would that not make you think the little moor folk were playing their tricks?
Worth, R. H. 1988, Worth’s Dartmoor, Newton Abbot: David & Charles Publishing