250
F. C. STEWARD
AND Η. Y. MOHAN RAM
yet, undefined biochemical features. Nevertheless, it is significant that
it is free cells—spores or gametes—that usually initiate complete new
cycles of growth. In tissue cultures the potentialities of the free cells for
organized growth far exceed that of a large tissue mass which continues
to be influenced by the organized core at its centre (Steward et al., 1959).
FIG. 6. Embryo-like Growth Forms in Cultured Cells, (a-d) Diagrammatic sketches
showing the formation of cell clusters from isolated cells of tobacco (after Bergman,
1959). (e~j) Similar sequence in carrot cells grown in liquid medium (after Steward,
Mapes and Mears, 1958).
The second requirement is for a medium competent to support the full
capacity of the freed cells to divide and grow—whether these cells are
totipotent parenchyma or the cells of an embryo. Both systems seem
to respond to the nutrient fluids that commonly nourish immature
embryos. When such free cells grow in a liquid medium it is surprising
F. C. STEWARD
AND Η. Y. MOHAN RAM
yet, undefined biochemical features. Nevertheless, it is significant that
it is free cells—spores or gametes—that usually initiate complete new
cycles of growth. In tissue cultures the potentialities of the free cells for
organized growth far exceed that of a large tissue mass which continues
to be influenced by the organized core at its centre (Steward et al., 1959).
FIG. 6. Embryo-like Growth Forms in Cultured Cells, (a-d) Diagrammatic sketches
showing the formation of cell clusters from isolated cells of tobacco (after Bergman,
1959). (e~j) Similar sequence in carrot cells grown in liquid medium (after Steward,
Mapes and Mears, 1958).
The second requirement is for a medium competent to support the full
capacity of the freed cells to divide and grow—whether these cells are
totipotent parenchyma or the cells of an embryo. Both systems seem
to respond to the nutrient fluids that commonly nourish immature
embryos. When such free cells grow in a liquid medium it is surprising