This type of lichen is a very good environmental quality indicator. Apart from its large surface area to volume ratio, the lichens containing cyanobacteria are very sensitive to air pollutants, especially sulphur dioxide, so they can be used to reveal the air condition. In some places, the lichens are also used to detect the presence of heavy metals in the environment. Indeed, I saw something like fruticose lichen in the Nursery Path of CUHK but I am not sure if it was a Tillandsia usneoides or a fruticose lichen at that time as they look similar to me.

Did you take a photo? You are welcome to upload the photo to biophotosharing and I can then find some experts to see what kind of lichen it is. It's good to know that CUHK has fruticose lichen :)

There is an interesting fact about fruticose lichen. Pseudevernia furfuraceae is a fruticose lichen, it is also called the mummy lichen as it was found on a female Egyptian mummy during the unwrapping process in 1859. Pseudevernia furfuraceae was purposely placed on the mummy’s body cavity before the burial for embalming as the lichen has preservative properties and aromatic properties.

Q) Are there any other use of fruticose lichen?

Fruticose lichen differ from other forms of lichen based on their bushy form that is attached to the ground only at the base of the lichen. The continuous algal layer that grows around the circumference of the branches of the lichen is the most important difference to distinguish fruticose lichen from other form of lichen. The thallus may be either rounded or flattened, unbranched or branched. Fruticose lichens have a fine, round, hair-like structures and are loosely attached to rocks and trees. Although fruticose lichens are defined as being bushy, they can also exhibit a flattened and strap-like appearance. Q) How do fruticose lichen reproduce?

Leung Hei Tung: Thanks for sharing the interesting fact
Lok Ching Tung: can I know the source of your information?