Bacidia and Bacidina
A genus of crustose species having a green alga; thallus thin, areolate, granular, immersed, or sorediate, mostly drab green, whitish, grey or brown colours; apothecia with a distinct excipular rim lacking algae, the cells mostly cylindrical and arrayed in a fan-like appearance as seen in cross section (Bacidia), or broadly elliptical, at least in the numerous outer layers (Bacidina); hymenium of straight, mostly unbranched paraphyses embedded in gel, upper portions colourless or with green, purplish or brown pigments; hypothecium colourless or brown; asci mostly narrowly cylindrical at maturity; spores 8, colourless, always transversely septate, usually with numerous septae, generally acicular or bacilliform, or fusiform in a few species.
References: Ekman 1996; Ekman 2004a, b.
| 1a. | Thallus of easily detached, corticate granules that remain opaque when wet …2 |
| 2a. | Thallus granules 50-200 µ wide; apothecia usually absent; upper hymenium with blue-green pigments; spores 25-47 × 1-4 µ; on rough bark and mosses of old trees where humid and well-lit; to be sought …[Bacidia bagliettoana (A. Massal. & De Not.) Jatta] |
| 2b. | Thallus granules 80-300 µ wide; apothecia common; upper hymenium colorless or pale orange; spores 31-104 × 2.1-4.3 µ …Bacidia rubella |
| 1b. | Thallus of areoles or granules, if granular, then granules weakly corticate and translucent when wet …3 |
| 3a. | Apothecia POL+ whitish crystals in the hymenium that react C+ pink-red (gyrophoric acid); asci ±Micarea-type …“Bacidia” beckhausii |
| 3b. | Apothecia C- in section, POL- or POL+ only in atop the hymenium, gyrophoric acid lacking; asci Bacidia-type …4 |
| 4a. | Spores (52‑) 69-96 (‑108) µ, with over 20 septae; rim glossy, deep cherry red, the disc a darker red-brown …Bacidia idahoensis |
| 4b. | Spores <70 µ long or, if longer, then with fewer than 20 septae; rim and disc black, brown, whitish, or purplish, but not deep red or red-brown …5 |
| 5a. | Upper hymenium with green, green-gray, purple, or purple-gray pigments, N+ purple-red …6 |
| 6a. | Rim formed of complicatedly netted hyphae, sections greatly swelling in K; upper hymenium greyish (K+ bluish green) or greyish-purple (K+ deep reddish purple); growing on decaying polypore fungi …“Bacidia” purpurea |
| 6b. | Rim formed of radiating hyphae, sections not much swelling in K; upper hymenium green or grey-green, K-; upper hymenium POL-; spores various; rarely on polypore fungi, common species, especially on Populus trichocarpa or bark of other nutrient-rich trees and shrubs …7 |
| 7a. | Hypothecium colourless to medium brown, K-; spores (11‑) 12-37 (‑45) × 1.7-3.5 µ; apothecial rim generally persistent …Bacidia circumspecta |
| 7b. | Hypothecium light to dark brown, K+ purplish; spores (19‑) 23-50 (‑64) × 2-5 µ; apothecial rim generally receding with maturity …Bacidia subincompta |
| 5b. | Upper hymenium purple-brown, brown, orangish or colorless, N- or N+ brown or orange-red …8 |
| 8a. | Upper hymenium dingy purple brown, K+ purple; apothecia high-convex young or old, often becoming tuberculate, the rim thin and quickly receding; spores 18-24 × 2-3 µ …Bacidia cf. vermifera |
| 8b. | Upper hymenium lacking purple tones, K- or K+ other colors; apothecia not becoming high-convex or tuberculate, the rim persistent or receding; spores various …9 |
| 9a. | Apothecial rim with a distinct algal layer visible in section, at least in young apothecia; apothecia whitish beige, usually translucent when wet, the algal layer often visible within; spores (25‑) 31-49 (‑57) × 1.5-2.5 µ …Bacidina ramea |
| 9b. | Apothecia lacking algae, not distinctly translucent when wet; spores various …10 |
| 10a. | Thallus of white areoles; outer portion of exciple light to medium brown, K+ orangish brown; hypothecium pale to light brown, K+ yellow-brown; spores 35-47 × 0.8-1.2 µ; growing on polypore fungi; to be sought …[Bacidia polyporae Björk ined.] |
| 10b. | Thallus of inconspicuous goniocysts or of dark olive-green areoles; exciple not K+ orangish; hypothecium not K+ yellowish; spores and habitat various various …11 |
| 11a. | Thallus conspicuous, extensive, waxy, corticate, drab olive; apothecia waxy orange-beige, over 0.2 mm wide at maturity, the rim and disc roughly the same colour; spores 30-45 (‑50) × 1-2 µ; growing on smooth bark of shrubs, mostly in subalpine forest …Bacidina contecta |
| 11b. | Thallus usually inconspicuous, of goniocysts, pale to medium fresh-green; apothecia various; spores various; limited to lower elevation habitats …12 |
| 12a. | Hypothecium distinctly darker than the hymenium (except in rare shade forms); apothecia up to 0.5 mm wide, the rim almost always paler than the light to medium pink-brown disc; spores (30‑) 39-42 (‑48) × 1-2 µ …Bacidina arnoldiana |
| 12b. | Hypothecium pale, not distinctly pigmented; apothecia up to 0.3 mm wide, the rim paler than or concolorous to the disc; spores various …13 |
| 13a. | Overgrowing moribund arboreal cyanolichens; exciple complete below the hypothecium; spores 30-35 × 0.8-1 µ; common in humid forest …Bacidina sp. A |
| 13b. | Known only from decaying polypore fungi; exciple interrupted by the stipe-like hypothecium; spores about 25 × 1.2 µ …Bacidina senilis |
Bacidia circumspecta (Nyl. ex Vainio) Malme
Thallus deep green, warty, granular or smooth, inconspicuous and usually intermixed with other lichen thalli, containing trebouxioid algae; apothecia bluish black, 0.3-0.7 mm wide, the rim prominent and persistent; exciple formed from parallel, somewhat fanning hyphae with narrow, straight-sided lumina, lacking crystals, usually green and K+ purplish in the outer layer and brownish within; hymenium 45-75 µ, with scattered vertical streaks of dingy greenish pigment; upper hymenium dark dingy bluish green, K- or K+ purplish, N+ pink-red or purple; hypothecium colourless to medium brown, K+ browner; spores bacilliform, straight or slightly curved, 12-35 × 1.7-3 µ, with 3-7 septae.
Reactions: All thalline spot tests negative.
Contents: No known lichen substances.
Habitat: Nutrient-rich bark in shady forests. Lower to middle elevations.
Similar Species: Bacidia subincompta is very similar and grows in the same habitats, but has mostly larger apothecia, larger spores, and a darker hypothecium.
Local Status: Common.
Specimens: Björk 12119, 12221.
Bacidia idahoensis H. Magn.
Thallus areolate, olive-green or grey-green, waxy or somewhat glossy; apothecia glossy, with a thick, deep red-brown rim and dark brown to blackish disc; hymenium 90-130 µ high, upper portions pigmented medium to dark reddish brown, K+ purplish, N+ orange-red, the lower portions and the hypothecium colourless or pale yellow-brown; spores long-bacilliform, straight or slightly curved, 60-100 × 2.5-3.5 µ, with about 20 septae.
Reactions: Spot tests all negative.
Contents: No known lichen substances.
Habitat: On conifer branches and twigs in wet forests, especially on nutrient-rich surfaces, e.g., within the dripzone of large Populus trichocarpa. Lower to middle elevations.
Similar Species: No other local species bears large apothecia with a thick, glossy deep red-brown rim. The apothecia of Lecanora rufocincta ined. are similarly coloured, but differ in being smaller and matte. This species also grows on acidic bark and wood.
Specimens: Björk 13959.
Local Status: Occasional.
Bacidia rubella (Hoffm.) A. Massal.
Thallus of corticate, olive-green or grey-brown granules 70-300 µ wide, the cortex with regularly spaced papillae (LM); apothecia orange-brown, with a thick, sometimes whitish-pruinose, prominent rim that recedes with overmaturity; hymenium 70-100 µ high, colourless or pale yellow-brown; hypothecium colourless or pale yellow-brown; spores acicular, curved or sigmoid, 40-65 × 2.5-3.5 µ, with 3-9 septae.
Reactions: Thallus K- or K+ yellow.
Contents: Sometimes with significant amounts of atranorin.
Habitat: On rough bark of broadleaf trees where humid but well-lit. Lower elevations.
Similar Species: See notes under Agonimia sp.
Specimens: Björk 12282.
Local Status: Rare.
Bacidia subincompta (Nyl.) Arnold
Thallus of granules or areoles, deep fresh green, usually intermixed with other lichen thalli, and thus often difficult to observe, containing a trebouxioid alga; apothecia bluish black 0.4-1.0 mm wide, usually glossy, the rim prominent and persistent, the disc usually remaining flat; exciple formed of parallel, fanning hyphae with narrow lumina, the outermost part often green, otherwise dark to light brown; hymenium 55-100 µ high, colourless or with scattered green streaks; upper hymenium usually dark bluish-green, often with additional brown pigments, K- or K+ purplish, N+ pink-red or purple; hypothecium medium to dark brown, topping a paler region below, K+ purplish, N+ orange-red; spores long bacilliform, or sometimes acicular, straight or slightly curved, 25-50 × 2-5 µ wide, with 3-10 septae.
Reactions: All thallus spot tests negative.
Contents: No known lichen substances.
Habitat: Almost always on Populus tremuloides (aspen), or on Pseudotsuga in aspen dripzones, but also on decaying acidic bark of shrubs and Betula papyrifera. Lower to middle elevations.
Similar Species: Bacidia circumspecta, B. punctiformis, and B. vermifera are similar in appearance, but have shorter spores and paler hypothecia.
Specimens: Björk 10779.
Local Status: Common.
Bacidia cf. vermifera (Nyl.) Th. Fr.
Thallus mostly continuous and smooth, sometimes lumpy or granular, containing a trebouxioid alga; apothecia black, somewhat glossy; the rim prominent and persistent and the disc usually flat (ours with a thin, receding rim and domed disc); exciple dark brown in the exterior layer, grading to pale brown within; hymenium 50-65 µ high; upper hymenium dark (reddish) brown, K+ purplish, N+ orange-red; hypothecium colourless or pale brown; spores worm-shaped, with rounded ends, mostly curved or S-curved (ours straight or weakly curved), 20-43 × 2-3 µ.
Reactions: All thallus spot tests negative.
Contents: No known lichen substances.
Habitat: Branches and trunks of Betula and Populus trichocarpa. Lower elevations.
Similar Species: Bacidia circumspecta and B. subincompta appear similar, but have distinct green pigments in the upper hymenium.
Local Status: Uncommon.
Notes: Differs from true B. vermifera in having straight or weakly curved spores and a quickly receding rim.
Bacidina arnoldiana (Körb.) V. Wirth & Vězda
Thallus of areoles that disintegrate into non-corticate granules with maturity, the thallus becoming entirely granular, pale green or grey-green; apothecia pink, orangish pink, greyish pink, reddish brown, or dark grey-brown, the rim thin but persistent, usually paler than the disc, the disc often mottled; hymenium 40-70 µ high, colourless throughout or light brown in upper portions; hypothecium colourless or, more often, light to medium brown; spores straight or moderately curved or sigmoid, 35-45 × 1-1.6 µ, with 1-9 septae.
Reactions: Spot tests all negative.
Contents: No lichen substances known.
Habitat: On branches and twigs of conifers and, less often, broadleaf trees in humid forests, especially in waterfall spray zones and along whitewater rivers; often also in Populus trichocarpa dripzones. Lower to middle elevations.
Similar Species: Bacidina ramea has smaller apothecia that remain pale pink and have a less persistent rim.
Specimens: Björk 8772, 12393; Goward 04-30.
Local Status: Occasional.
Bacidina contecta S. Ekman ined.
Thallus dark khaki-green; apothecia numerous, usually solitary but sometimes in 2’s and 3’s, 0.3-0.6 mm across; disc flat to low-convex, whitish tan, margined when young by a translucent proper rim that becomes obscure with maturity; apothecial rim composed of cells with lumina all roughly the same size (in contrast to the unevely enlarged lumina of the similar species Bacidina delicata); asci 8-spored; spores needle-shaped (acicular), straight or sigmoid, colourless, many-celled, 30-45 × 1-1.5 µm.
Reactions: All spot tests negative.
Contents: No known lichen substances.
Habitat: Bark of deciduous shrubs within the winter snowpack at upper, rarely middle, elevations.
Similar Species: In Bacidina delicata the cells of the proper rim have unequally enlarged lumina: those of the outer portions are wider than those of the inner portions. Some upper elevation Biatora and Lecidea species may appear similar, but lack the combination of a dark khaki green crust and whitish tan apothecia; nor do they have needle-shaped spores.
Local Status: Common.
Notes: Known only from inland BC, northern Idaho, and northwest Montana.
Bacidina ramea Ekman
Thallus of areoles or granules, pale grey, yellowish grey or greenish grey, often inconspicuous; apothecia pale pink to medium brown, the rim with a distinct algal layer that at first is a thalline layer, but later gets tucked under the exciple as it develops; hymenium 55-65 µ high, unpigmented or light brown in upper portions; hypothecium unpigmented; spores acicular, straight or slightly curved, 30-50 × 1.5-2.2 µ.
Reactions: Spot tests all negative.
Contents: No lichen substances known.
Habitat: On rain-sheltered conifer twigs in humid forests. Lower to middle elevations.
Similar Species: Bacidina arnoldiana has larger apothecia that often become dark-pigmented, with a paler, more persistent rim.
Specimens: Björk 10895, 13227.
Local Status: Occasional.
Notes: This is the only member of Bacidia/Bacidina with algae in the apothecial rim.
Bacidina senilis Björk ined.
Thallus of pale to medium green granules, mostly seen around the apothecia; apothecia 0.15-0.3 (‑0.4) mm wide, pale pinkish or pale to light pinkish brown, the rim thin and receding with age; exciple of elliptical cells, forming a ring around the stipe-like base of the hypothecium; hymenium colourless or pale to light brown in upper portions; hypothecium colourless; spores about 25 × 1.2 µ, straight or slightly curved, with 2-5 septae.
Reactions: Spot tests all negative.
Contents: Unknown
Habitat: On decaying polypore fungi in swamp forests. Lower elevations.
Similar Species: “Bacidia” purpurea and Bacidia polyporae also grow over decaying polypore fungi, but both have darker apothecia with narrowly cylindrical hyphae in the exciple.
Specimens: Björk 14412.
Local Status: Rare.
Notes: Currently known only from the study area.
Bacidina sp. A sensu Spribille
Thallus granular, bright green or light green, sometimes inconspicuous and film-like; apothecia pale yellowish pink, with a thin but persistent rim; exciple of large, elliptical cells; hymenium 40-50 µ high, unpigmented, lacking crystals; hypothecium colourless; spores acicular, curved or sigmoid, 29-40 × 1.2-1.4 µ.
Reactions: Spot tests all negative.
Contents: No known lichen substances.
Habitat: Known only from decaying Nephroma on conifer twigs and branches in humid forests. Lower to middle elevations.
Similar Species: Pale forms of Bacidina arnoldiana have larger apothecia and larger spores. Bacidina ramea may also appear similar, especially older apothecia in which the thalline rim has receded; it can be recognized by the presence of algae tucked into the base of the exciple in section.
Specimens: Björk 14412.
Local Status: Occasional.
Notes: Known only from inland BC and northwest Montana.
“Bacidia” purpurea Björk ined.
Thallus of areoles and small corticate granules, pale grey-green or creamy green; apothecia dark purplish grey, with a thick, persistent rim that thickens greatly prior to the maturation of the disc, becoming gyrose with age; exciple swelling greatly in K, formed of narrowly cylindrical hyphae densely branched and anastomosing, the lumina not expanding in size outward toward the edge; hymenium colourless except in upper portions, where purplish-gray and K+ reddish purple, or greenish-gray and K+ bluish green, also with fine POL+ crystals; paraphyses abruptly swollen at the tip to about 4 µ wide; hypothecium colourless, formed of intricately branched and anastomosed hyphae, very thick; spores 25-40 × 1.5-1.8 µ, acicular, moderately curved or sigmoid.
Reactions: Spot tests all negative.
Contents: Unknown
Habitat: On decaying polypore fungi on Alnus stems in swamps. Lower elevations.
Similar Species: Bacidia polyporae and Bacidina senilis also grow on decaying polypores, but in neither species does the apothecial pigmentation have purplish undertones, nor are the exciple and hypothecium made up of intricately netted hyphae.
Specimens: Björk 12429, 14280, 17845.
Local Status: Rare.
Notes: This distinctive species probably does not belong in Bacidia or in Bacidina, differing in the structure of the exciple and in apothecial development. Known only from the study area.