144
LUISE STANGE
is needed about the metabolic relationships between meristematic and
permanent cells or between adjacent cells in an isolated plant part which
behave differently during embryonization.
IV. Differentiation of Regenerates
The conditions under which a regenerate differentiates can be very
different from the conditions in normal development. The differentiation of the regenerate may, in certain cases, give some information about
influences coming from the isolated part at which the regenerate is
formed, or about the properties of the regenerating cell itself.
A. Differentiation under Influence of the Isolated Part
This mode of regeneration is realized in all cases of regeneration after
injury of single cells. Here, regeneration is not combined with nuclear
and cell division but the lost parts of the cell are replaced under complete control of the surviving part of the cell. One example of this type
of regeneration is offered by the unicellular and uninucleate green alga
Acetabularia, which is specially suitable for regeneration experiments
because of its length, reaching up to several centimetres. When the
stalk of the plant is amputated, the rhizoid containing the nucleus of the
cell forms a new membrane at the cut surface and regenerates a new
stalk in complete continuity with the isolated cell part after a few days
(Hämmerling, 1934). (The extensive investigations on nuclear-cytoplasmic relationships in the development of Acetabularia, carried out by
means of regeneration, go beyond the scope of this article ; cf. Hämmerling, 1953, 1963.) Another example of regeneration after injury of a
single cell has been studied in cytological detail in Vaucheria (Weissenböck, 1939). After subdividing the protoplast of the cell by plasmolysis,
the cells restored themselves by the formation of new membranes.
In multicellular lower plants no comparably strong control is exerted
on a regenerate from the part at which it arises. Unlike higher plants,
lower plants do not show the phenomenon of wound healing, where the
regeneration process is also under complete control of the injured plant.
At first sight the regenerates in multicellular lower plants seem to be
completely independent of the isolated part and to be a copy of the
individuals of normal development which originate from a single cell.
Thus, it has been rightly pointed out, after extensive comparative
investigations in liverworts (Fulford, 1956) and mosses (Noguchi and
Muraoka, 1959), that the pattern of development of regenerates is
similar to that of the sporeling of the same species, while the pattern of
regenerative development in different species may vary greatly. But
on closer examination, several cases of the whole isolated part influencing
LUISE STANGE
is needed about the metabolic relationships between meristematic and
permanent cells or between adjacent cells in an isolated plant part which
behave differently during embryonization.
IV. Differentiation of Regenerates
The conditions under which a regenerate differentiates can be very
different from the conditions in normal development. The differentiation of the regenerate may, in certain cases, give some information about
influences coming from the isolated part at which the regenerate is
formed, or about the properties of the regenerating cell itself.
A. Differentiation under Influence of the Isolated Part
This mode of regeneration is realized in all cases of regeneration after
injury of single cells. Here, regeneration is not combined with nuclear
and cell division but the lost parts of the cell are replaced under complete control of the surviving part of the cell. One example of this type
of regeneration is offered by the unicellular and uninucleate green alga
Acetabularia, which is specially suitable for regeneration experiments
because of its length, reaching up to several centimetres. When the
stalk of the plant is amputated, the rhizoid containing the nucleus of the
cell forms a new membrane at the cut surface and regenerates a new
stalk in complete continuity with the isolated cell part after a few days
(Hämmerling, 1934). (The extensive investigations on nuclear-cytoplasmic relationships in the development of Acetabularia, carried out by
means of regeneration, go beyond the scope of this article ; cf. Hämmerling, 1953, 1963.) Another example of regeneration after injury of a
single cell has been studied in cytological detail in Vaucheria (Weissenböck, 1939). After subdividing the protoplast of the cell by plasmolysis,
the cells restored themselves by the formation of new membranes.
In multicellular lower plants no comparably strong control is exerted
on a regenerate from the part at which it arises. Unlike higher plants,
lower plants do not show the phenomenon of wound healing, where the
regeneration process is also under complete control of the injured plant.
At first sight the regenerates in multicellular lower plants seem to be
completely independent of the isolated part and to be a copy of the
individuals of normal development which originate from a single cell.
Thus, it has been rightly pointed out, after extensive comparative
investigations in liverworts (Fulford, 1956) and mosses (Noguchi and
Muraoka, 1959), that the pattern of development of regenerates is
similar to that of the sporeling of the same species, while the pattern of
regenerative development in different species may vary greatly. But
on closer examination, several cases of the whole isolated part influencing