Leptolyngbya purpurascens (Gomont ex Gomont) Anagnostidis et Komárek

Thallus compact, leathery, purple to brownish violet. Filaments strongly bent, entangled. Sheaths initially visible, thin, later ± incompletely diffluent. Trichomes dark violet to bluish violet, 1.5-2.5 um wide, not constricted at the cross-walls, not attenuated at the ends, straight. Cells almost isodiametric or up to nearly 5x longer than wide, 2—4.5 (10) um long; cell content characteristically marked with two granules on either side of cross-walls. Apical cells rounded, without calyptra.
Occurrence: Freshwater, epilithic on stones in not cold cataracts, on calcareous (always?) rocks, and slightly thermal springs; known from France, Germany (Baden), Italy (Eugano); out of Europe: N America (Yellowstone Nat. Park), N Africa, Chile, India, Japan. Heterogeneous species from which were described (under Phormidium) several subspecific taxa (varieties), which should be revised, e.g.: Phormidium purpurascens var. circinatum Virieux 1911: trichomes 3.7-3.9 um wide, tightly screw-like coiled; incompletely described, possibly represents an Arthrospirai; P. purpurascens var. homogenea Gardner 1927: it is either identical with Leptolyngbya purpurea (Gomont) Anagnostidis et Komarek or represents a special species (e.g., Leptolyngbya homogenea (Gardner) Anagnostidis 2001); P. purpurascens var. laminatum Copeland 1936: thallus lamellated, interspaced with slimy layers, up to 1 cm thick, purplish brown. Trichomes 1-1.4 um wide, ^heaths mostly confluent. Cells 2-4x longer than wide, 2-6 urn long. Identical With type or special species?
Komárek J., Anagnostidis K. Cyanoprokaryota. II. Oscillatoriales // Süsswasserflora von Mitteleuropa. Bd. 19 (2). München, 2005. 759 p.