11 RESEARCH NOTES TGC REPORT No . 31, 1981 experiments and experiments with whole plants were performed to confirm previous reports and to attempt to achieve phenotypic reversion of the pds phenotype . Tomato var's VF - 36, VF - 145, and var . VF - 36 with pds/pds as well as the L . pimpinellifolium seeds used in these experiments were obtained from Dr . C . M . Rick, University of California, Davis, through Dr . John Fobes . Seeds were germinated by placing them on basic MS medium (Murashige and Skoog, 1962 Physiol . Plant . 15:473 - 479) . The plants were allowed to grow for 10 days on this medium . Hypocotyls were excised and placed, 4 per plate, onto MS medium supplemented with 8 . 9µM benzyl - adenine and 10 . 8µM napthaleneacetic acid in 100 x 15 mm plastic petri plates (33 ml volume) . Callus was grown for 30 days in the light with a 16 hour day, at 70 E sec - 1 m - 2 , at 25° C . Rapidly growing callus was removed from the outside edge of the developing mass and subcultured onto fresh medium . After another 30 days of growth, pieces were taken from these calli for the experiments . The growth of callus was monitored during these experiments by individually weighing each of the 4 pieces of callus which were used in each replicate plate, then weighing each of them at the end of the experiment . All of the experiments were done with 10 replicate plates per treatment unless otherwise noted . The plates were sealed with parafilm to prevent dessication for the duration of the experiments, which was