Contribution to the microscopic study of three plant species used in traditional Algerian medicine

The present work aims to study the anatomical characteristics of three plant species used in Algeria for their diuretic and antilithiasic properties. Also to summarise the results obtained in detailed drawings of each part studied as well as diagrams with conventional tissue signs. 
For this, plant samples were collected from herbalists in the region of Tlemcen (northwestern Algeria). These were leaves and stems of Petroselinum crispum (Apiaceae), leaves of Scolymus hispanicus (Asteraceae), leaves and stems of Marrubium vulgare (Lamiaceae); they were all examined and identified. Cross sections were made and stained using the double staining technique; they were then observed under an optical microscope. 
It was generally observed that the parsley leaf did not have any secretory trichomes, and the secretory duct in the midrib was located between the phloem and the lower epidermis. It was also noted that there were no secretory trichomes in the Spanish Scolyme. In addition, branched covering trichomes and secretory trichomes with octacellular head were observed in the leaf of white horehound. 
These findings are certainly going to help enrich the rare bibliographic data available on the anatomy of these three species.