Two herbaceous species belonging to genus Solanum namely, Solanum melongena L. and Solanum lycopersicum L. were subjected to study the incidence of the secondary growth and consequently the formation of protective tissues in their roots. The main results were as follows : 1- At an early stage of growth, the xylem tissue at the base of the root accomplished a proportion of its final amount that was decidedly bigger than that needed for the shoot system already achieved by the plant. 2- In contrast to the eggplant, no development of any periderm-like structure at the periphery of the root of tomato was detected. In the successive ages, storage depletion of food stuff in root parenchyma of the eggplant was not found in the tomato root. 3- The whole vascular cylinder was dissected into differently sized sectors by rays of varied width ranging in cross section from 2 to 6 cells. This histological characteristic was not present in the root of eggplant. 4- The root xylem in the tomato root unlike that in the eggplant looked heterogeneously perforated.