ABSTRACT

The genus Ocimum is characterized by a great variability of both morphology and chemotypes. The case of cross-pollination leads to a large number of subspecies, varieties and forms. These morphological differences are evidenced in plant height, leaf colour and leaf dimension. The aim of this study is to delimit four putative hybrids of 0. gratissimum and also to differentiate these 0. gratissimum hybrids from Hyptis suaveolens with which it is commonly confused by field workers. Analysis of the characters of the epidermis revealed the immense value of some foliar epidermal characters to the taxonomy of H. suaveolens and 0. gratissimum complex. These characters included the isodiametric shape of the epidermal cells of hybrid A and epidermal glands on the epidermis of 0. gratissimum hybrids. The different types, shape and sizes of trichomes in both genera were also of significant importance. Anatomically significant features were observed in the leaf lamina, stem and root. These included multicellular epidermal hairs seen on the adaxial epidermis of hybrids C and D and on the epidermis of H. suaveolens. Multicellular hairs were also observed on H. suaveolens. Circularly arranged, outer metaxylem vessels occur in hybrids B. The result of palynological studies reveal the grains of hybrid D to be circular in shape and significantly different from other complex and H. suaveolens which have elliptical shaped grains. Calcium oxalate crystals occurred in all the taxa studied, these crystals which are in aggregates occurred mostly within the ground tissue of the leaves, stems and roots of all the taxa investigated. The result of this study, when combined with the gross morphology, could aid field workers in resolving the confusion in the identification of Hyptis suaveolens and 0. gratissimum complex, which are economically important plants.