Easily mis-identified as :
Marchantia liverwort species, but they lack the smooth surface of the thallus ('leaves') typical of those found in liverworts of the Pellia Genus. They also lack the 'umbrella spokes' of Marchantia.
The capsules (not shown) are produced on short lived stalks (hyaline), and have four longitudinal valves which open to release the spores.
Neels' Pellia is not as common as
Dripwort (Pellia epiphylla) but is nevertheless fairly frequent in the UK, mainly to the west, or north of England and Scotland.
THE UNUSUAL VIOLET COLOURATION
The above specimen is not the normal colour for Pellia species, and a plausible explanation, put forward by two people independently (one, the Author), is that the liverwort may be reacting to a substance in the soil to create the violet colouration in the veins. The author himself thinks that some metallic mineral in the soil may be replacing magnesium in the porphyrins (either chlorophyll itself, or some derivative of it). Porphyrins with metallic centres are highly coloured. Haemoglobin has a single atom of iron at the centre, and when oxygenated (to oxyhaemoglobin) is bright red. Another haem-like compounds found naturally is the manganese-based
Pinnaglobin found in a mollusc and which is brown. On the other hand, the abnormal purple coloration may simply be due to some anthocyanin pigments changing colour in response to pH differences in the soil, however, the author can find no mention of anthocyanins within Pellia species. So the puzzle of the purple coloration remains; it is mysterious.
The author came across the violet-coloured anthocyanidin
Riccionidin A (and its dimer
Riccionidin B) in the literature. This is a most unusual
anthocyanidin, for it has an extra 5-membered furan ring (or you could think of it as a bridging
ether linkage across two parts of the anthocyanidin, but either way, it is most unusual).
The dimer of Riccionidin A, left, is Riccionidin B, below. It is possible that the linkage between the two monomer units occurs at either the [3'-3'] position (as shown) or at the [5'-5'] position; it was not possible to differentiate between the two possibilities from the NMR spectrum.
The Author is not suggesting that these molecules explain the coloration in the above photographs, merely that it might be possible that they could. Neither Riccionidin A nor Riccionidin B have ever been reported as occurring in Pellia species, but they have been found in several other Liverworts (Marchantiophylla), namely in Ricciocarpos natans, Marchantia polymorpha, Riccia duplex and Scapania undulata. However, none of those liverworts have such overtly manifest purple colorations as in the above photos. The formation of these cell-wall pigments in these specimens is dependent upon both the light intensity and the nutrient levels, the formation favouring lower phospate and sucrose levels but higher nitrogen levels.
So, the puzzle of the violet coloration in Nees' Pellia remains.
This bryophyte has the largest spermatozoid of all the bryophytes.
This thallose (leafy) liverwort unusually smells aromatic, but tastes intensely pungent and acrid. It contains several aromatic compounds and diterpene dialdehydes such as
Sacculatal (18-hydroxy-7,16-sacculatadien-11,12-dial; which is a prenyldrimane) being one of the latter that has been identified. Sacculatal is a dialdehyde which can induce contact dermatitis, tastes hot and is the means by which it protects itself against being eaten by insects. Both Sacculatal and the stereoisomer
IsoSacculatal are present in this Liverwort, as well ss several other dialdehydes which deter feeding.
Various other sacculatanes occur in other Liverworts, such as in
Porella perrottetiana and
Trichocoleopsis sacculata, from which the compound derives its name. These Liverworts are all strongly sharp-tasting and thus anti-feeding, and all may induce contact dermatitis. They contain derivatives of Sacculatal such as 7,17-sacculatadiene-11,12-dial which promotes tumors.