Crustose Lichens at Barwinnock Herbs

Crustose Lichen Diversity

Introduction to Crustose Forms of lichen:

Both fertile and sterile forms are found:

Rhizocarpon geographicum

Rhizocarpon geographicum
Rhizocarpon geographicum on a roadside, South facing boulder

Thallus smooth and thin but having a distinct green/yellow colour.

UV light gives a bright orange fluorescence.

Rhizocarpon reductum ?

Rhizocarpon reductum
Rhizocarpon reductum on West facing boulder of the cattle pens

Thallus smooth, hard and thin. Apothecia 0.5mm dia, black with raised black margin.

Tests with K and C negative.

Doubt over identification as Dobson 2011 p 393 states thallus usually 1-2cm.

Porpidia macrocarpa ?

Porpidia macrocarpa
With large black apothecia on South facing sandstone. C+red test shown.

Large apothecia 1.5 to 3mm convex and without a margin but cracks around the outside and across the middle of many. Not in concentric circles. Some rust coloured patches.

Thallus soft and areolate (cracked into small paving stone sections). Surface partially with soridea. Prothallus cream.

Not Rhizocarpon petraeum: apothecia too large and no concentric pattern. Identification doubt because test with calcium hypochlorite positive red. (C+red.) Test with potassium hydroxide dark green (K+green).

Baeomyces rufus

Baeomyces rufus
Baeomyces rufus on North facing partially sheltered stone dyke

Minute mushroom shaped (podetia) with white stalk and brown apothecia. 1mm dia and 2mm high.

Thallus light green/ grey

Pertusaria corallina

Pertusaria corallina
Pertusaria corallina on West facing stone dyke

White/light grey crust with a rough and powdery surface caused by a covering of short, rounded isidia.

Test with potassium hydroxide solution yields a clear yellow indication. K+y

Pertusaria pseudocorallina

Pertusaria pseudocorallina
Pertusaria pseudocorallina on West facing stone dyke

White/light grey crust with a rough and powdery surface caused by a covering of short, rounded isidia.

Test with potassium hydroxide solution yields a clear red indication. K+r