140
A. D. BONEY
arise from between the holdfast tissue and actively growing branches,
Hence if frondage is cut at a sufficient height from the ground regenerative growth from the remaining stumps will be possible, and also
from the basal shoots. It is also evident from observations made by
Baardseth on cut fronds that growth from lateral pits becomes noticeable 1 month after cutting as well as initiation of the base shoots, but
that after 5 months the new growths are not very long. The base and
stump shoots combined contribute to the new frondage. The base
shoots are initially long and slender, probably because of the reduced
light intensity in the holdfast region.
During the annual life of the plant, David (1943) observed that new
apical growth was initiated in October, but that afterwards little
elongation was noticeable for as long as the autumnal fruiting receptacles were produced, suggesting a shunting of metabolic products
accompanied by a decline in light and temperature. The first signs
of apical growth appeared on plants in the upper regions of the shore,
and then moved progressively down shore. Vesicle initiation was
observed in the following March, with one vesicle produced per
year. Marked apical growth of the frond was observed between
April and October, and lateral receptacular pits were laid down
on either side of the growing branch. With increasing age of the
branch only those receptacular pits in the youngest (distal) part of
the frond produced receptacles. The meristematic cells in the receptacular pits maintained their viability for a number of years, but
rarely more than 5 years. On the coast of Wales, David observed
vesicle production at the start of the 2nd year of growth, whilst Printz
(1926) stated that in Norway vesicle formation is not observed until
the 3rd year. There is evidence that a new branch must reach a certain
(minimum) fresh weight before vesicle formation is observed. The
period of rapid apical growth mentioned above is also the one in which
the most marked regeneration of new branches from cut fronds is to be
observed (Baardseth, 1955b). David (1943) observed that the angle of
the slope of the substratum influenced plant size, and that longer
frondage was observed with plants growing on flat substrata. Other
factors affecting the size of the plants included the degree of infestation
by the red algae Polysiphonia lanosa, which caused considerable
stunting of growth if present in appreciable quantities on the frond.
Printz (1950) measured both growth and dry weights of Ascophyllum
branches from Norwegian plants. In 1st-year branches growth and dry
weight increased throughout spring and early summer, and then
speeded up appreciably by autumn. Thence the dry weight values
decreased. In the 2nd year there was again an increase in spring and
A. D. BONEY
arise from between the holdfast tissue and actively growing branches,
Hence if frondage is cut at a sufficient height from the ground regenerative growth from the remaining stumps will be possible, and also
from the basal shoots. It is also evident from observations made by
Baardseth on cut fronds that growth from lateral pits becomes noticeable 1 month after cutting as well as initiation of the base shoots, but
that after 5 months the new growths are not very long. The base and
stump shoots combined contribute to the new frondage. The base
shoots are initially long and slender, probably because of the reduced
light intensity in the holdfast region.
During the annual life of the plant, David (1943) observed that new
apical growth was initiated in October, but that afterwards little
elongation was noticeable for as long as the autumnal fruiting receptacles were produced, suggesting a shunting of metabolic products
accompanied by a decline in light and temperature. The first signs
of apical growth appeared on plants in the upper regions of the shore,
and then moved progressively down shore. Vesicle initiation was
observed in the following March, with one vesicle produced per
year. Marked apical growth of the frond was observed between
April and October, and lateral receptacular pits were laid down
on either side of the growing branch. With increasing age of the
branch only those receptacular pits in the youngest (distal) part of
the frond produced receptacles. The meristematic cells in the receptacular pits maintained their viability for a number of years, but
rarely more than 5 years. On the coast of Wales, David observed
vesicle production at the start of the 2nd year of growth, whilst Printz
(1926) stated that in Norway vesicle formation is not observed until
the 3rd year. There is evidence that a new branch must reach a certain
(minimum) fresh weight before vesicle formation is observed. The
period of rapid apical growth mentioned above is also the one in which
the most marked regeneration of new branches from cut fronds is to be
observed (Baardseth, 1955b). David (1943) observed that the angle of
the slope of the substratum influenced plant size, and that longer
frondage was observed with plants growing on flat substrata. Other
factors affecting the size of the plants included the degree of infestation
by the red algae Polysiphonia lanosa, which caused considerable
stunting of growth if present in appreciable quantities on the frond.
Printz (1950) measured both growth and dry weights of Ascophyllum
branches from Norwegian plants. In 1st-year branches growth and dry
weight increased throughout spring and early summer, and then
speeded up appreciably by autumn. Thence the dry weight values
decreased. In the 2nd year there was again an increase in spring and