[On regeneration capacity of isolated single cells and small groups of cells of Riella helicophylla].

1. Isolated single cells of the basal part of the gemma of Riella helicophylla regenerate to whole plants. Late developmental stages of rhizoid initials divide earlier after isolation than young rhizoid initials and "normal cells" of the basal part. 2. In isolated groups of two cells composed of one rhizoid initial and one "normal cell" only the rhizoid initial divides, and it divides much sooner than it does as a single cell. 3. If in isolated groups of two cells from the basal part of the gemma the divided cell is killed immediately after division, the second cell of the group also divides, just as soon, in fact, as it would have if it had been isolated as a single cell. If the first divided cell is killed 7 days after division, the division of the second cell of the group is delayed by 6 days. 4. After isolation of single cells and of small groups of cells from old as well as from young tissue of the wing, cell division occurs earliest in the largest cell groupe and latest in single cells. The regenerates develop the more quickly the larger the isolated cell group from which they derive. 5. Cells in fragments isolated from young tissue divide sooner after isolation than cells in fragments from old tissue. However, single cells isolated from old tissue divide earlier than single cells from young tissue. 6. Light is a prerequisite for regeneration of single cells and of small groups of cells from the marginal region of the wing. Only in relatively large tissue fragments do some cells also divide in the dark. 7. The existence and nature of correlations between the cells of a regenerating tissue fragment are discussed.