The capacity of various carbohydrates to support growth of Japanese morning-glory callus in the dark over a 14-day period was examined. Sucrose was the most effective compound, but glucose, fructose, trehalose, maltose, cellobiose, raffinose and soluble starch supported significant growth. The callus remained alive in the presence of inulin, mannitol, inositol, methyl-α-glucoside and glycerol; while cells grown on galactose, mannose, sorbose, xylose, arabinose, melibiose, lactose, dextran, carboxy-methyl cellulose, sorbitol, galactitol, ethylene glycol were necrotic. Examination of the effects of these various carbon sources on the cell wall and cytoplasmic activities of acid invertase, trehalase, maltase, cellobiase, melibiase and lactase could not be correlated with the growth-promoting activity of their substrates. Extracellular hydrolysis of sucrose, trehalose, maltose, cellobiose, lactose, raffinose, and inulin occurred as a consequence of the presence of cell wall hydrolases in the morning-glory callus, and hydrolytic products could be detected in the medium.