REGENERATION IN LOWER PLANTS
133
from small cauloid regenerates or gemmulae, proliferation is markedly
slowed down till new rhizoids are formed. Incision of other cells does not
have the same effect. Occasionally, small cauloid regenerates do not
form rhizoids ; in this case their meristematic cells do not continue to
divide. In Cladophora, as already mentioned, single isolated cells produce at first a new rhizoidal cell, before the apical pole grows out.
Possibly, the large basal cells of the fern prothallium and their derivatives are superior to the subapical cells in respect to some prerequisites
for cell elongation and rhizoid formation.
B. The Location of Regeneration
In many investigations on regeneration by way of embryonization
attention has been paid to the location of regenerates. In experiments
with the liverwort Marchantia, Vöchting (1885) observed a strict polar
location of regenerates just behind the apical cut surface of thallus
fragments. He assumed that the polar regeneration of tissue fragments
is the result of a polarity of its individual cells. Polar regeneration was
also observed in various algae, for instance in Cladophora (Miehe, 1905;
Czaja, 1930; Schoser, 1956; cf. Section I I I , A, 1) and Enteromorpha
(Müller-Stoll, 1952; Dangeard, 1957). In experiments with ferns Linsbauer (1926) and Albaum (1938b) separated prothallia into apical and
basal portions by a transverse cut. The basal portions regenerated new
prothallia near the cut surface, while the apical portions only formed
rhizoids from its basal cells. In several investigations in mosses the
location of regenerates in isolated leaves was studied. In Physcomitrium
turbinatum protonematal regeneration was not confined to any particular part of the leaves (Meyer, 1942). In Funaria hygrometrica Bopp
(1955) found the distal end of detached leaves to be the predominant
region of regeneration, while in Tortula muralis it was the proximal part
of isolated leaves. In whole detached leaves of Splachnum ampullaceum
the middle region showed a higher number of regenerates than the
proximal and distal regions (von Maltzahn and MacNutt, 1958).
Noguchi and Miyata (1957,1958) examined the regeneration of detached
leaves in a great number of mosses. In most species regeneration took
place only, or predominantly, in the proximal area of the leaves. When
the detached leaves were cultivated in media of different p H values,
regeneration spread out to the middle or distal portion of the leaves in
the media most favourable to regeneration (i.e. where the highest
number of regenerative filaments was produced). According to Gemell
(1953) the regeneration of isolated leaves in Atrichum undulatum is
restricted to the distal region and to the adaxial surface cells of the
midrib not bearing photosynthetic filaments. Near the tip of the leaf the
number of these cells is higher. A restriction of regeneration to special
E
A.M. 4
133
from small cauloid regenerates or gemmulae, proliferation is markedly
slowed down till new rhizoids are formed. Incision of other cells does not
have the same effect. Occasionally, small cauloid regenerates do not
form rhizoids ; in this case their meristematic cells do not continue to
divide. In Cladophora, as already mentioned, single isolated cells produce at first a new rhizoidal cell, before the apical pole grows out.
Possibly, the large basal cells of the fern prothallium and their derivatives are superior to the subapical cells in respect to some prerequisites
for cell elongation and rhizoid formation.
B. The Location of Regeneration
In many investigations on regeneration by way of embryonization
attention has been paid to the location of regenerates. In experiments
with the liverwort Marchantia, Vöchting (1885) observed a strict polar
location of regenerates just behind the apical cut surface of thallus
fragments. He assumed that the polar regeneration of tissue fragments
is the result of a polarity of its individual cells. Polar regeneration was
also observed in various algae, for instance in Cladophora (Miehe, 1905;
Czaja, 1930; Schoser, 1956; cf. Section I I I , A, 1) and Enteromorpha
(Müller-Stoll, 1952; Dangeard, 1957). In experiments with ferns Linsbauer (1926) and Albaum (1938b) separated prothallia into apical and
basal portions by a transverse cut. The basal portions regenerated new
prothallia near the cut surface, while the apical portions only formed
rhizoids from its basal cells. In several investigations in mosses the
location of regenerates in isolated leaves was studied. In Physcomitrium
turbinatum protonematal regeneration was not confined to any particular part of the leaves (Meyer, 1942). In Funaria hygrometrica Bopp
(1955) found the distal end of detached leaves to be the predominant
region of regeneration, while in Tortula muralis it was the proximal part
of isolated leaves. In whole detached leaves of Splachnum ampullaceum
the middle region showed a higher number of regenerates than the
proximal and distal regions (von Maltzahn and MacNutt, 1958).
Noguchi and Miyata (1957,1958) examined the regeneration of detached
leaves in a great number of mosses. In most species regeneration took
place only, or predominantly, in the proximal area of the leaves. When
the detached leaves were cultivated in media of different p H values,
regeneration spread out to the middle or distal portion of the leaves in
the media most favourable to regeneration (i.e. where the highest
number of regenerative filaments was produced). According to Gemell
(1953) the regeneration of isolated leaves in Atrichum undulatum is
restricted to the distal region and to the adaxial surface cells of the
midrib not bearing photosynthetic filaments. Near the tip of the leaf the
number of these cells is higher. A restriction of regeneration to special
E
A.M. 4