148
LUISE STANGE
The two new growth forms regenerated from the young sporogonium,
namely callus and seta growth, could be separated and cultivated
further without loss of their characteristic growth form. For the maintenance of callus growth it was important to cultivate the callus in the
light. In darkness the cells of the callus culture elongated and formed
protonema. But when this protonema was exposed to light after 2
weeks, all its apical cells changed again into the spherical shape characteristic of callus growth. On the other hand, when osmotically active
substances were added to the medium, the callus differentiated into sporogonia. Also the stage of sporogonial organization could be preserved in
permanent culture by continuously isolating zone B 2 of the newly
formed sporogonia and thus subculturing an unchanged physiological
state. In a special strain, derived from a spore of a hybrid capsule PiHy,
it was possible to maintain the sporogonial differentiation indefinitely
without continuous subculturing. The regenerated sporogonia formed
new seta tips as lateral branches and in this way the sporophytic stage
was propagated indefinitely.
These observations are interpreted to show that the regions of the
developing sporogonium which are still mainly embryonic, in so far as
their cells are active in division, preserve their specific state through and
beyond regeneration. The cells in the extreme tip are still completely
embryonic and continue to grow without differentiation after isolation.
In the adjacent zone (B 2 ), the seta is beginning to differentiate; the
new properties of these cells persist in the regeneration process, and
direct formation of sporogonia results. In the basal parts of the seta, the
factors responsible for sporophytic differentiation are either no longer
active or are destroyed during the process of regeneration. In protonema
regenerating from the transition zone between B 2 and C some factor for
sporogonial differentiation must be preserved and becomes effective at
the time of bud formation. I t could be shown that this factor, although
surviving the regeneration process, is labile. When the protonema was
isolated and transferred to fresh medium before the apogamous sporogonia were formed, only buds of the leafy moss plants were produced.
On the other hand, the factor can be stabilized for several months, when
the protonema regenerated from the transition zone is cultivated on 4%
agar (relatively dry conditions) or after addition of 0-01-0-1 M glucose.
Its latent existence can then be proved by transferring some protonema
to the normal agar medium or to liquid substrate. After this treatment
only sporogonia are produced.
The question is : what is the nature of this factor or the factors preserved in regeneration ? The observation that the factor can persist in many
subcultures of the protonema in a latent state, excludes the possibility
that a hormone-like substance has passed from the sporogonium cells to
LUISE STANGE
The two new growth forms regenerated from the young sporogonium,
namely callus and seta growth, could be separated and cultivated
further without loss of their characteristic growth form. For the maintenance of callus growth it was important to cultivate the callus in the
light. In darkness the cells of the callus culture elongated and formed
protonema. But when this protonema was exposed to light after 2
weeks, all its apical cells changed again into the spherical shape characteristic of callus growth. On the other hand, when osmotically active
substances were added to the medium, the callus differentiated into sporogonia. Also the stage of sporogonial organization could be preserved in
permanent culture by continuously isolating zone B 2 of the newly
formed sporogonia and thus subculturing an unchanged physiological
state. In a special strain, derived from a spore of a hybrid capsule PiHy,
it was possible to maintain the sporogonial differentiation indefinitely
without continuous subculturing. The regenerated sporogonia formed
new seta tips as lateral branches and in this way the sporophytic stage
was propagated indefinitely.
These observations are interpreted to show that the regions of the
developing sporogonium which are still mainly embryonic, in so far as
their cells are active in division, preserve their specific state through and
beyond regeneration. The cells in the extreme tip are still completely
embryonic and continue to grow without differentiation after isolation.
In the adjacent zone (B 2 ), the seta is beginning to differentiate; the
new properties of these cells persist in the regeneration process, and
direct formation of sporogonia results. In the basal parts of the seta, the
factors responsible for sporophytic differentiation are either no longer
active or are destroyed during the process of regeneration. In protonema
regenerating from the transition zone between B 2 and C some factor for
sporogonial differentiation must be preserved and becomes effective at
the time of bud formation. I t could be shown that this factor, although
surviving the regeneration process, is labile. When the protonema was
isolated and transferred to fresh medium before the apogamous sporogonia were formed, only buds of the leafy moss plants were produced.
On the other hand, the factor can be stabilized for several months, when
the protonema regenerated from the transition zone is cultivated on 4%
agar (relatively dry conditions) or after addition of 0-01-0-1 M glucose.
Its latent existence can then be proved by transferring some protonema
to the normal agar medium or to liquid substrate. After this treatment
only sporogonia are produced.
The question is : what is the nature of this factor or the factors preserved in regeneration ? The observation that the factor can persist in many
subcultures of the protonema in a latent state, excludes the possibility
that a hormone-like substance has passed from the sporogonium cells to