REGENERATION IN LOWER PLANTS
149
the regenerative protonema. After separation of the protonema from the
sporogonium section there would be no further supply of this substance
and it would become diluted and finally lost in the large number of cell
divisions during protonema growth. I t must be assumed, therefore,
that the factor is able to propagate itself in each protonema cell.
Two alternatives are discussed by Bauer (1961b, 1963). Either we are
dealing with plasmatic structures capable of self-reproduction or the
continuous production of the factor in question is due to the stabilization of a certain combination of genes in an active state. In the case of
the sporogonial factor being propagated in the protonema, these genes
(or gene) would become effective only when the conditions for the formation of buds are realized. Gametophore and sporogonium have in common an axial structure by which they are distinguished from the protonema stage. The factors responsible for the formation of this axial
structure seem to be still unspecific and must apparently be supplemented by other factors for the special organization of the gametophore
or the sporogonium.
Different quality of the regenerates depending on the stage of
differentiation of the regenerating cells has also been reported for the
fern Adiantum pedatum by Morel (1963). Normal diploid sporelings and
leaves of adult plants, both grown in aseptic culture, were cut into small
pieces and cultured in the same manner. While the pieces from the young
leaves proliferated into prothallia, some of the epidermal cells in the
fragments of the adult leaves formed at first a callus of undifferentiated
parenchyma. When these calluses were transferred to fresh medium,
they soon became organized and produced numerous sporophytes with
apical meristems, leaves and roots. The author assumes that, during the
process of ageing, the factor leading to the production of gametophytic
tissue, still present in juvenile leaves, has been lost. These results cannot be compared directly with those of Bauer, since important morphological and physiological differences exist between the sporophytes of
bryophytes and pteridophytes.
I n other experiments on regeneration in fern sporophytes, the
different quality of regenerates could not be related to the stage of
differentiation of the regenerating cell. From stem segments of the fern
Phlebodium aureum, regular production of both gametophytic and sporophytic plants were observed (Ward, 1963). The two forms of regenerates
occurred immediately adjacent to each other, but the pattern of origin
was different. Gametophytes were preceded by filamentous regenerates,
while sporophytes arose from an accumulation of a cellular mass. I t was
not reported, whether differences existed between the regenerating cells
which gave rise to these two completely dissimilar states of differentiation. On the other hand, it is known from other investigations, that the
149
the regenerative protonema. After separation of the protonema from the
sporogonium section there would be no further supply of this substance
and it would become diluted and finally lost in the large number of cell
divisions during protonema growth. I t must be assumed, therefore,
that the factor is able to propagate itself in each protonema cell.
Two alternatives are discussed by Bauer (1961b, 1963). Either we are
dealing with plasmatic structures capable of self-reproduction or the
continuous production of the factor in question is due to the stabilization of a certain combination of genes in an active state. In the case of
the sporogonial factor being propagated in the protonema, these genes
(or gene) would become effective only when the conditions for the formation of buds are realized. Gametophore and sporogonium have in common an axial structure by which they are distinguished from the protonema stage. The factors responsible for the formation of this axial
structure seem to be still unspecific and must apparently be supplemented by other factors for the special organization of the gametophore
or the sporogonium.
Different quality of the regenerates depending on the stage of
differentiation of the regenerating cells has also been reported for the
fern Adiantum pedatum by Morel (1963). Normal diploid sporelings and
leaves of adult plants, both grown in aseptic culture, were cut into small
pieces and cultured in the same manner. While the pieces from the young
leaves proliferated into prothallia, some of the epidermal cells in the
fragments of the adult leaves formed at first a callus of undifferentiated
parenchyma. When these calluses were transferred to fresh medium,
they soon became organized and produced numerous sporophytes with
apical meristems, leaves and roots. The author assumes that, during the
process of ageing, the factor leading to the production of gametophytic
tissue, still present in juvenile leaves, has been lost. These results cannot be compared directly with those of Bauer, since important morphological and physiological differences exist between the sporophytes of
bryophytes and pteridophytes.
I n other experiments on regeneration in fern sporophytes, the
different quality of regenerates could not be related to the stage of
differentiation of the regenerating cell. From stem segments of the fern
Phlebodium aureum, regular production of both gametophytic and sporophytic plants were observed (Ward, 1963). The two forms of regenerates
occurred immediately adjacent to each other, but the pattern of origin
was different. Gametophytes were preceded by filamentous regenerates,
while sporophytes arose from an accumulation of a cellular mass. I t was
not reported, whether differences existed between the regenerating cells
which gave rise to these two completely dissimilar states of differentiation. On the other hand, it is known from other investigations, that the