Taxonomic revision of the genus Heliotropium (Boraginaceae s.l.) in south Yemen

摘要: The flora and fauna of Arabia, particularly southern Yemen, has recently attracted the interest many authors. In this study, genus Heliotropium L. (Boraginaceae) is taxonomically revised in Yemen. Ten species are recognized. Nomenclature, typification, representative specimens a diagnostic key to all provided, along with their distribution most valuable characters those flowers (calyx, corolla, androecium gynoecium) nutlets, thoroughly investigated discussed. Both light scanning microscopy used investigation. Papillate anther apices (brush-like) were recognized some species. Connate anthers deep or shallow ventral circular depressions on nutlets found be useful distinguishing members H. sect. Orthostachys (viz. strigosum, rariflorum ovalifolium), while winged only pterocarpum. length hairiness style stigma also proved useful.