The accumulation of anthocyanin by clones and subclones from a cell suspension culture of wild carrot (Daucus carota L.) has been measured under standard conditions. Clones which accumulate low amounts of anthocyanin were shown, by recloning after maintenance by serial passage, to have become heterogenous and to contain cells with increased accumulation of anthocyanin. There appears to be a maximum amount of anthocyanin that clones can accumulate. Clones which accumulate the maximum amount of anthocyanin were shown by recloning after maintenance by serial passaging, to have become heterogenous and to contain many cells which accumulate less than the maximum possible amount of anthocyanin. When clones which accumulate the maximum amount of anthocyanin are maintained by serial passage, the decline in anthocyanin accumulation is different in different media. The results indicate that the changes in the ability of cells to accumulate anthocyanin involve no qualitative change in the genetic information of the cells, i.e., the changes are not the consequence of mutations.

Previously it has been found that in tobacco callus cells nucleolar vacuoles repeatedly form and contract. In this study, nucleolar vacuoles were investigated by using radioautography, actinomycin D, and electron microscopy . It was found, from grain counts of nucleoli labeled with uridine 3H, that nucleoli containing vacuoles had more than three times as many grains/µ 2 of nucleolar substance as did nucleolei without vacuoles . Treatment of tobacco callus cells with various concentrations of actinomycin D caused the percentage of cells containing nucleolar vacuoles to decrease ; with the highest concentration the percentage of these cells dropped from the normal level of about 70 % o to less than 10 % . However, after removal of actinomycin D the cells regained nucleolar vacuoles up to the control level . When radioautography was used with actinomycin D, it was found that the actinomycin D inhibited the uptake of uridine-3H, i .e . inhibited RNA synthesis, in those nucleoli which lost their nucleolar vacuoles . In addition, after removal of the cells from actinomycin D, it was found that as the cells regained nucleolar vacuoles the nucleoli also began to incorporate uridine-3 H. Electron micrographs showed the nucleoli to be composed of a compact, finely fibrous central portion surrounded by a layer of dense particles 100-150 A in diameter . Nucleolar vacuoles occurred in the fibrous central portion . Dense particles similar to those in the outer layer of the nucleoli were found scattered throughout the vacuoles and in a dense layer at their outer edge . These data suggest that in cultured tobacco callus cells the formation and contraction of nucleolar vacuoles is closely related to RNA synthesis in the nucleolus .

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