Interfilum R. Chodat.

Interfilum cells are solitary or attached to each other with mucilage forming short filaments. The individual cells are round to ellipsoid, surrounded by a twolayered cell wall, and possess lobed, parietal chloroplasts with pyrenoids (Fig. 30). During division, the daughter cells form within the mother cell wall (Ettl & Gärtner 2013). According to Rindi et al. (2011), Interfilum is nested within Klebsormidium . This aerophytic genus currently harbours three accepted species (Guiry & Guiry 2022). Interfilum is the only known lichen-forming lineage of the Streptophyta . Interfilum massjukiae and Interfilum sp. were reported from Placynthiella spp. and Micarea prasina as secondary photobionts based on morphological observations. The same algal species were also found to grow epiphytically on the surface of lichen thalli (Voytsekhovich et al. 2011). Free-living I. massjukiae was observed on the surface of pyroclastic outcrops in Crimea, Ukraine (Mikhailyuk et al. 2008).