An Léicean
Tá dá chuid i léicin, cuid algach agus cuid fungasach agus braitheann siad ar an mbáisteach le taise a fháil. Ós rud é go ngoilleann truailliú go mór ar léicin is comhartha é go bhfuil an t-aer go maith má bhíonn siad le feiceáil ar na crainn i mbaile mór. Má bhíonn siad mór agus cuma toir orthu is cosúil go bhfuil an t-aer ar fheabhas.
Lichen
Lichens comprise an algal part and a fungal part, and are dependent on rainwater for moisture. Since lichens are particularly sensitive to air pollution, their condition, when they occur on town trees, indicates air quality. The bigger, shrubbier the lichen, the healthier the air.