Thelocarpon
Crustose lichens or unlichenized saprobic or parasitic fungi, when lichenized, containing a chlorococcoid alga; thallus, if present, smooth, granular or immersed; apothecia resembling perithecia, often globose and opening by a small pore, sometimes initial perithecium-like but later widening and exposing the disc, whitish or covered in bright yellow pruina, the rim formed of a thin layer of more or less parallel hyphae tightly packed without much of a gel layer between; hymenium formed of more or less straight and unbranched paraphyses weakly embedded in gel; hypothecium colourless; asci thin-walled, more or less pear-shaped IKI- or + pale blue with a darker blue tube in a modestly thickened tholus; spores about 50-300 per ascus (or 8 in T. pallidum), colourless, simple or with a single septum (3-9 septae in T. pallidum), elliptical, oblong or bacilliform.
References: Purvis et al. 1992; Knudsen & Lumbsch 2007.
| 1a. | Thallus of areoles, or immersed; apothecia globose, perithecioid, deep yellow, not stalked, usually lacking a usually with a yellow pruina; spores about 200 per ascus, oblong, simple, 4-7 (‑12) × 1.7-2.5 (‑3) µ; starting as a parasite on moribund lichens, especially on green Peltigera spp., sometimes later independent; common and widespread …Thelocarpon epibolum |
| 1b. | Thallus of few goniocysts or not apparent; apothecia cup-shaped, with a slight stalk, the disc exposed, white, lacking pruina; spores 8 per ascus, elliptical, 3- to 9-septate, 20-25 × 8-10 µ; uncommon [Note: the placement in Thelocarpon is preliminary pending further work] …Thelocarpon pallidum ined. |
Thelocarpon pallidum Björk ined.
Thallus a very thin, colourless film, intertwined with or overgrowing other thalli at least in part, also growing over mosses, occurring with lichenized cyanobacteria, trebouxioid and trentepohlioid algae, sometimes producing a few goniocysts; apothecia whitish, translucent when wet, individually isolated or somewhat crowded, 0.05-0.1 mm wide, with a short stalk at the base, the wall thin and inconspicuous but persistently cupping the disc, formed of strictly ascending hyphae conglutinated in thin gel, the disc low-convex and flush with the top of the wall; rim non-algal, formed of parallel, vertical hyphae 3-6 µ wide, at the stipitate base, the hyphae converge from the thallus and ascend together to form the stalk and the rim; hymenium 110-120 µ high, lacking gel; upper hymenium undifferentiated, lacking pigments, gel and crystals; hypothecium colourless; paraphyses sparsely branched or simple, not entwining the asci; asci 110-120 × 15-20 µ, thin-walled throughout; spores 8 per ascus, elliptical, colourless, most slightly curved, the outer walls slightly constricted at the 3 septae, 20-25 × 8-10 µ.
Reactions: All spot tests negative.
Contents: Unknown.
Habitat: Overgrowing other lichens (Nephroma, Placynthiella and Placynthium) on a decaying log and on fissured bark of a Populus trichocarpa trunk. Lower elevations.
Similar Species: No other crust lichen in the study has minute, stalked, unpigmented apothecia.
Specimens: Björk 13785.
Local Status: Rare.
Notes: This strange little crust may not belong in Thelocarpon, having only 8-spored asci and 3-septate spores, but the apothecial structure and habitat are similar. Known only from inland BC.
Thelocarpon epibolum Nyl.
Thallus immersed, lacking algae, or a scarcely evident algal film around the base of the apothecia; apothecia about 0.1 mm wide, spherical or obconic, covered in bright yellow pruina, the outer wall 15-30 µ thick, formed of ascending hyphae covered in crystals; hymenium 110-135 µ high, colourless, I+ orangish red, IKI+ blue; spores about 100-200 per ascus, simple, oblong and often slightly constricted around the middle, 4-7 × 1.7-2.5 (‑3) µ.
Reactions: All spot tests negative.
Contents: Vulpinic acid, pulvinic dilactone, and ± pulvinic acid.
Habitat: Usually growing over decaying green-algal Peltigera species on the ground, less often on other lichens, or on moist wood or bark. Lower elevations.
Similar Species: Unmistakable for the minute, bright yellow, globose apothecia and the habitat.
Specimens: Björk 13202.
Local Status: Occasional.