| TAXON: | Lathagrium auriforme (With.) Otálora, P.M. Jørg. & Wedin (2013) |
| RECENT SYNONYMS: | Collema auriforme (With.) Coppins & J.R. Laundon (1984) |
| FAMILY: | Collemataceae |
| GROWTH FORM: | Foliose, homoiomerous (gelatinous) |
| SUBSTRATES: | Highly calcareous rock, mortar, soil and shell-sand |
| PHOTOBIONT: | Nostoc cyanobacterium, in chains |
| REPRODUCTION: | Isidia; rarely apothecia, pycnidia |
| ASCUS: | If present, clavate; apex thickened, with K/I+ pale-blue tholus and deep-blue downward tubular structure; 8 spores |
| SPORES: | Ascospores if present ellipsoidal to ovoid, submuriform, 26-36 × 8.5-13 µm; conidia if present bacilliform |
| NOTABLE FEATURES: | Thallus dark brown with olive tinge, gelatinous, swollen when wet, wrinkled when dry; lobes few, loose, reminiscent of ears; isidia globose, abundant, crowded, often obscuring thallus |
| CHEMICAL TESTS: | – |
| HABITAT: | In damp, shady situations, often amongst mosses |
| DISTRIBUTION: | Widespread across Britain, often common |
| CONSERVATION STATUS: | Least Concern |
| LICHENICOLOUS FUNGI: | Didymellopsis pulposi, Endococcus caudisporus |
| IDENTIFICATION DIFFICULTY: | Green 1: Field identification possible |
| CONFUSION SPECIES: | Lathagrium fuscovirens, Scytinium plicatile |
FIELD NOTES
Lathagrium auriforme is one of the so-called ‘jelly lichens’, and it can be recognised on sight once you’re familiar with it. Wet and well-developed specimens seem to bubble over with spherical isidia, to the point that the lichen appears like a oily tapioca pudding. Where the lobes of the thallus are visible, they often look like little ears: hence the species name auriforme.
If you’re not familiar with jelly lichens, you might confuse L. auriforme with L. fuscovirens or Scytinium plicatile. These two species can also have abundant spherical isidia covering the thallus. But there are fairly easy ways to differentiate them all in the field.
L. fuscovirens has distinctly smaller, more uniform isidia, and it doesn’t become as pulpy when wet. Compared to L. auriforme, it appears more matt and, thanks to its smaller isidia, even a bit scruffy. It also tolerates drier and more exposed habitats, so the location of your specimen might provide another clue.
S. plicatile doesn’t swell when wet like L. auriforme. Rather, it remains cartilaginous or rubbery.
LAB NOTES
Lathagrium auriforme can normally be identified without microscopy.
SPECIMENS
Lathagrium auriforme : Scotland : VC98 Argyll : NM8300 : August 2024 : On mortared stone wall : © Anthony Speca : CC BY-SA 4.0
