Figure 2 from: Rikkinen J (2013) Molecular studies on cyanobacterial diversity in lichen symbioses. MycoKeys 6: 3-32. https://doi.org/10.3897/mycokeys.6.3869

Figure 2 - Free-living and lichen-symbiotic Nostoc strains. A Free-living Nostoc colonies and gelatinous cyanolichens (Collema sp.) growing on mineral soil in northern Spain B Free-living Nostoc colony on limestone in northern Italy C Lichenized Collema thallus (containing Nostoc symbionts) on limestone in northern Italy D–F Morphological variation of Nostoc symbionts inside two Leptogium thalli in southwestern Kenya. The large clear cells are nitrogen-fixing heterocysts, the smaller translucent structures are fungal hyphae in optical cross-section.