Abstract: The Mediterranean basin has a great diversity of plant species and constitutes a point of great interest for any scientific study, whether biological or ecological, due to its vast wealth and the heterogeneity of historical, geological and ecological factors.\r\nA rich variety of medicinal plants grows around this basin, including Barbary Thuya, subject of our study. It is an endemic species of North West Africa (Morocco, Algeria and Tunisia). Most of the Tetraclininis area is situated in a temperate semi-arid and warm bioclimatic level.\r\nThe anatomical study enables us to know internal organization and structures of primary and secondary plants, various organs, as well as their modifications or adaptations. It remains one of the most essential parts of plant biology. It also allows making useful comparisons between existing plants [1].\r\nUnfortunately, in Algeria and more specifically in the North-West region, namely in Tlemcen�s littoral matorral, no study has been published on the anatomical and histometric characteristics of Tetraclinis articulata, despite being an endemic species in this area.\r\nInsofar as no precise data on tissues anatomy and measurements are available, we have tried to make a contribution by providing a brief survey of the forms and the average size of the various organs tissues (leaves, stems and roots).\r\nAs a first step, we have tried to give an overview on the average size of the observed Tetraclinis articulata tissues, and as a second step, we tried to advance some ecophysiological explanations concerning ten feet that have been chosen randomly, in the same region of Tlemcen but in two different stations (Honaine and Beni Snous).\r\nOur work is aiming to carry out a comparison between the different tissues structures, differentiate between different organs, use the anatomical sections for a statistical treatment and consequently to interpret explanation of certain histological phenomena as possible adaptations of the plant to environmental constraints such as water stress, climate change ... etc. This requires making microscopic sections from suitably chosen samples. As for any histological approach, four successive stages are necessary: The choice of the material to be studied; the technique that will allow to visualize the targeted structures or phenomena; producing images of these structures or phenomena by optical means, both the interpretation of these images and the methods used in histology vary according to the samples to be studied and the study objectives.\r\nThe histological study reveals an adaptation that we have noticed in Thuya, based on activity alternation between the tissues of the leaf, the stem and the root, here expressed by the correlation coefficient between them.\r\nTo develop a better understanding of Thuya�s behavior, we have calculated the correlation coefficient between the different tissues measured for statistical calculations, which helped us to better interpret the obtained results.