## 3 Results
### Lichen Morphology
#### 3.2.2 Scanning Electron Microscopy  
Scanning electron microscopy (SEM) is an optimal hybrid method for examining lichen thalli at high resolution [34], showing the micro-morphology of _U. barbata_ thallus layers [35]. The obtained SEM images combined the optical microscopy visualization performance and facility with high-resolution electron microscopy [36]. Thus, the morphological characteristics were easily identified in all ground _U. barbata_ samples with particle sizes around 315 \(\upmu\)m. The SEM micrographs are displayed in Figures 3 and 4. Figure 2: Microstructure of unground _U. barbata_ lichen thallus—FM images with different magnifications: 100\(\times\) (**a**) and 400\(\times\) (**b,c**). Figure 4: SEM micrographs in \(d\)UB (particle size > 315 \(\upmu\)m): (**a–c**) cortex fragments, central cord, and fungal hyphae, at different magnifications: (**a**) 1 k\(\times\) (scale bar = 20 \(\upmu\)m), (**b**) 2 k\(\times\) (scale bar = 20 \(\upmu\)m), (**c**) 5 k\(\times\) (scale bar = 5 \(\upmu\)m); (**d–f**) central cord with fungal hyphae between cortex fragments, at different magnifications: (**d**) 200 k\(\times\) (scale bar = 200 \(\upmu\)m), (**e**) 1 k\(\times\) (scale bar = 20 \(\upmu\)m), (**f**) 5 k\(\times\) (scale bar = 5 \(\upmu\)m). Figure 3: (**a–d**) Microstructure of the central cord (\(cc\)UB) with particle size > 315 \(\upmu\)m, in SEM images with different magnifications: (**a**) 300\(\times\) (scale bar = 100 \(\upmu\)m), (**b**) 1 k\(\times\) (scale bar = 20 \(\upmu\)m), (**c**) 2 k\(\times\) (scale bar = 20 \(\upmu\)m), (**d**) 5 k\(\times\) (scale bar = 5 \(\upmu\)m); (**e–h**) SEM micrographs of \(mc\)UB (medulla– cortex) with particle size \(\leq\) 315 \(\upmu\)m: (**e**) cortex parts with rare fungal hyphae on the surface, 1 k\(\times\) (scale bar = 20 \(\upmu\)m), (**f–h**) cortex fragment at different magnifications: (**f**) 1 k\(\times\) (scale bar = 20 \(\upmu\)m), (**g**) 2 k\(\times\) (scale bar = 20 \(\upmu\)m), (**h**) 5 k\(\times\) (scale bar = 5 \(\upmu\)m). Figure 3 shows SEM images of the central cord, _cc_UB (particle size \(>\) 315 \(\upmu\)m), and medulla-cortex, _mc_UB (particle size \(\leq\) 315 \(\upmu\)m). The SEM micrographs of _cc_UB (Figure 3a-d) were obtained at the following magnifications and scale bars: 300\(\times\) (scale bar = 100 \(\upmu\)m), 1 k\(\times\) (scale bar = 20 \(\upmu\)m), 2 k\(\times\) (scale bar = 20 \(\upmu\)m), 5 k\(\times\) (5 \(\upmu\)m). The cartilaginous structure of the central cord can be observed and, on its surface, free fungal hyphae (Figure 3a,b). This particular structure of the central axis and the aspect of free fungal hyphae are detailed in Figure 3c,d at 2 k\(\times\) and 5 k\(\times\) magnification (scale bar = 20 \(\upmu\)m and 5 \(\upmu\)m). In _mc_UB (particle size \(\leq\) 315 \(\upmu\)m), cortex fragments with a compact structure and rare fungal hyphae can be seen (Figure 3e-h). On the surface of fungal hyphae, secondary metabolite crystals can be observed (Figure 3e). In _Usnea_ lichens, usnic acid is the most common secondary metabolite in high concentrations; for this reason, usnic acid is commonly indicated in the corresponding figures [37]. Figure 3f-h displays a cortex fragment at different magnifications: 1 k\(\times\) (scale bar = 20 \(\upmu\)m), 2 k\(\times\) (scale bar = 20 \(\upmu\)m), 5 k\(\times\) (scale bar = 5 \(\upmu\)m). At high magnifications, the structural differences between the central axis and cortex (both constituted by fungal hyphae)--which are the basis of their different properties--can be observed. In _d_UB (particle size \(>\) 315 \(\upmu\)m), we can identify the morphology of _U. barbata_ thallus: central cord parts, cortex fragments, and rare fungal hyphae (Figure 4a-c). An isolated fragment of the central axis can be observed at different magnifications (Figure 4d-f). The structures of both layers (central cord and cortex) formed by mycelial hyphae are essential, supporting dried lichen separation in _cc_UB and _mc_UB fractions.