Liverworts of Derbyshire - part 2

In the Peak District, identification is easy, as this is the only Radula found in this region (and the only species in most of England & Wales). 

The very similar R.lindenbergiana is a largely subalpine species, distinguished by its dioicous, rather than monoicous reproduction; the exact identity of non-fertile plants cannot be determined.

It can be recognised by its upturned leaf margins and large size.

It has a very glossy appearance and closely appressed leaves which curl downwards when dry (as in this photo).  An unusual, but reliable, test in the field is to taste a tiny stem tip - this is the only British Porella to have an acrid, spicy taste, not unlike raw chilli!

When viewed closely, the leaf lobes are pointed, whereas F.dilatata has rounded leaf lobes.

F. dilatata has rounded, broad leaf lobules. 

In the Peak District, as in most of Britain, this is an exclusively epiphytic species.

It grows on a few shaded, sheer limestone rock faces in ash woodland in Matlock Bath, as well as a limited number of other sites. 

M.mackaii can be easily recognised by its very flat appearance and almost black stems, although new growth is pale green, as shown here.

L.cavifolia has closely overlapping leaves and large underleaves (unlike L.lamacerina below).  This isn't always easy to see in some specimens, so microscopical analysis is the most reliable way to separate species - the cells of the leaf apex and far more abundant and persistent cellular oil bodies being distinctive for L. cavifolia.

Unlike L.cavifolia (above) it is largely saxicolous (rock-dwelling), and only rarely grows on trees. 

Both species are found in shady woodland, although L. lamacerina tends to be found in wet, rather than merely humid habitats.

C.calyptrifolia is a characteristic species on the humid north and west of our country, and the few recorded occurrences in the western Peak District mark the species' south-eastern limit in Britain.  In the Peak District it is a rare, epiphytic species, often on willow, but further west it also grows on rock faces. 

I apologise for the poor photo, but this is a very tricky little liverwort to photograph!

C. rossettiana is the least common of the three species, and is very similar to C. calcarea.  Both grow on shaded limestone and need microscopical analysis of the abaxial leaf lobule surfaces - these are smooth in C. calcarea and spiny in C. rossettiana.  The perianths and bracts are also different in the two species.

See the description of C. rossettiana above for features of the two species.

As a genus, Fossombronias are easily recognised by their resemblance to tiny lettuces (in my opinion). 

Four species are found in the Peak District, although only this species and F.pusilla are widespread.

It is a base-rich habitat species, growing in wet areas such as rock faces, by streams and on the floor of quarries (as here). 

The two other British Pellia species are absent from base-rich habitats.

P. neesiana is much less common than the other two species in Derbyshire, and is almost entirely restricted to the Dark Peak.

It forms creeping mats, always sparsely branched, unlike some other similar thallose liverworts such as Pellia sp.

It favours wet habitats (the colony photographed here was growing on a flushed, gently sloping hillside).  This species and the fairly common R. chamaedryfolia are very similar, and microscopical examination of the cell oil bodies is necessary to be absolutely certain of the plant's identity.

Although very similar to M. consanguinea (below), it can be readily distinguished when fertile by the location of the gemmae at the tips of the branches only, rather than along the margins.

image coming soon!
Coombs Dale SSSI

Its distinctive characteristic of gemmae along the thallus margins can be seen clearly in the top half of this photo especially. 

Like M.violacea, this species is epiphytic.

By and large a northern species, M. pubescens reaches its southern English limit in the Peak District, where it can be found fairly regularly in calcareous woodland on humid limestone crags.


Cressbrook Dale NNR

Deep Dale NR

In Coombs Dale it grows on exposed south-facing steep limestone rock faces which are very dry in the summer. 

This species superficially resembles R.hemisphaerica (in my opinion), but is generally a darker, non-glaucous, green and has a narrower, more parallel-sided thallus.  The best feature for distinguishing the two plants is to see them when fertile though - T.hypophylla bears its reproductive receptacles on the underside of the thalli, which are distinctively black.  When dry, the thalli of this species roll up along their length, and the plant looks like a group of black worm-like tubes - a feature which no other British liverwort shares.


Coombs Dale SSSI

The Latin name of this species derives from the shape of the female reproductive organs, which are borne on short stalks.

Mill Dale

R.hemisphaerica also grows in similar habitats in Derbyshire (although it favours drier sites), and has purple-tinged thallus margins, but the surface of its thalli are smooth and lack the reticulate pattern.

Sporophytes

The median groove of this species is a sharp, narrow V-shape - a useful identification feature when combined with the glaucous grey-green colour and thallus proportions.

Coombs Dale SSSI

The thalli are long and thin, pale yellowish-green and have a shallow, flat-bottomed median groove (unlike the sharper groove of some other species). 

In favoured sites, the tiny rosettes of this species can cover large areas of bare soil.  When these plants were photographed, there were literally hundreds, if not thousands of individuals along the reservoir margin.

The species also occurs much more rarely on soil ledges in limestone dales.