LIPETZ, JACQUES. (Rockefeller Inst., New York, N. Y.) Calcium and the control of lignification in tissue cultures. Amer. Jour. Bot. 4!J(5): 460-464. lIlus. 1!J62.-Crown-gall tissues of Helianthus, Parthenocissus, Nicotiana, habituated Nicotiana, normal carrot, and Parthenocissus tissues grown in vitro on media low in calcium show an increase in lignification. The lignin is deposited not only o i the walls of tracheids but on the walls of parenchymatous cells as well. Transferring the tissues to media containing higher calcium concentrations inhibits this excess lignification. Neither s.rontium nor magnesium could be substituted for calcium. These studies indicate that the availability and concentration of inorganic ions playa role in the control of lignification.