Pericarp structure of Leucas and related genera (Lamiaceae subfam. Lamioideae)

The pericarp has been studied in 72 taxa belonging to the genera Leucas, Leonotis, Acrotome, Otostegia and Isoleucas. Otostegia, Isoleucas and many Leucas (the Asiatic sections Astrodon, Leucas, Plagiostoma , and the African Spiculifolia, Squarrosicyme, Stachydiformis and Virgata ) have been found to agree with most other members of the subfamily Lamioideae by having high bone cells which contain crystals. Acrotome, Leonotis and most African Leucas (sections Hemistoma, Lasiocotys, Lonostoma, Neuflizeana, Ogadenia and Physoleucas ) deviate by having thin bone cells which often lack crystals, and due to their similarity, these African taxa are suggested to be closely related. The Asiatic Leucas (Ortholeucas), Plagiostoma and Astrodon also seem to form a group. Leucas milanjiana and perhaps also Leucas hyssopifolia are considered to be extraneous to Plagiostoma and to be more closely related to the section Leucas and the African Lasiocorys, Ogadenia and Physoleucas respectively.