Serial sections of mature stems of ten species of herbaceous dicotyledonous plants were examined by light microscopy and the number of chloroplasts per cell was estimated in epidermis, collenchyma and cortex. Chloroplast identification was made by both light and transmission electron microscopy. Chloroplasts were present in epidermis, collenchyma and cortex tissues of all stems examined. The smallest number of chloroplasts was observed in the epidermis. Collenchyma cells had the largest number of plastids in four of the genera and cortex cells had the largest number in the remaining six genera. The stem epidermis of all genera contained stomates as demonstrated by scanning electron microscopy and aceto-orcein stained epidermal peels.