Fruticose lichen is the most sensitive group lichen to air pollution as it has a large surface area to volume ratio, so it can be used to monitor the air quality. Although from this slide, no distinct algal layer is formed, we can observe the algal cells which are the round cells in dark color showing in the middle of the bottom picture.

Here I have a question. What are the large masses in black on both sides of the upper picture? Are they the pack of hyphae or just contamination?

Qian Na: good description and observation!