Anatomical study of four species of Heliotropium L. (Boraginaceae) from Saudi Arabia

The leaf anatomy and distribution of types of foliar trichome of four Heliotropium L. species have been investigated. The aim of this study is to evaluate the systematicrelevance of their diversity compared to the recent findings of systematic relationshipswithin the genus. The results of leaf anatomy patterns, especially venation, vascularsystem, various types of foliar trichome and localization of crystals are surprisingly of high systematic value and proof.   Key words: Heliotropium L., leaf anatomy, Kranze-cells, C3 and C4 plants, venation, stomata, trichomes, crystals.