Air pollution is one of the most serious problems in the world. Other than natural sources, air pollution can also result from human activity; the level of atmospheric pollution has reached the dimensions that threaten human health due to the rapid urbanization and the increase of number of vehicles in the market, which are considered as the main emission sources of important quantities of toxic substances in the atmosphere that can remain intact in nature for long period affecting human, animals but also plants. The livings beings are the reflection of the environment in which they evolve and their observation in various levels of biological organizations can offer indications about the quality and the characteristics of that environment, therefore, the study of the bioaccumulation of xenobiotics in exposed organisms represents an important way of assessing pollution’s level. Due to the absence of root system, and due to their bio-accumulating power, lichens and bryophyte are, since decades, used as bio-indicator of air pollution. In this paper we tested an in vitro contamination of two cryptogrammic species, known for their bioaccumulation power, by different concentrations of lead; a lichenic species "Xanthoria parietina" and muscicole species "hylocomium splendens”, collected from the region of Bir El Djir "Oran ", in order to characterize their bio accumulating power of lead, as well as the impact of the different concentrations of that xenobiotic on their physiological parameters. This study allowed as to identify the perturbation of the different physiological parameters in lichen "Xanthoria parietina" and bryophyte "hylocomium splendens”. These changes were correlated with the important contents of lead accumulated by both thalli, from solutions in which the two species were exposed.