154
A. D. BONEY
of Aswphyllum nodosum fronds similarly had a harmful effect, suggesting production by Aswphyllum of substances toxic to the Laminuria
sporelings.
9. Taxonomic observations on Laminaria species
More recent works on the taxonomy of Laminaria species have
tended to show overlapping of the specific characters of some entities.
Parke (1948) pointed out that growth forms of L. saccharina were
obtainable which could be fitted to the description of other distinct
species (e.g. L. hieroglyphiea, L. faroensis, L. longicruris). The need
was shown for more data on chromosome numbers, and for transplant
experiments. Sundene (1962) has shown how the forms of L. digitata
can be modified by environmental conditions. Burrows (1964) has
reviewed the more significant diagnostic characters of Laminuria
species, (e.g. shape of base of blade; blade texture and condition of
margin ; presence or absence of mucilage ducts), together with appearance of the meristoderm cells in surface view (Wilce, 1959). I n a
comparative study of European forms of L. saccharina cultured at
5°C and 10°C and of plants of similar forms from Nova Scotia which
failed to show all of the main characters of L. saccharina, the two forms
were found to be quite distinct in shape and size, even to size of cells
of the gametophytes. However, continued growth of plants of L.
saccharinu at the lower temperature resulted in marked differences in
its specific characters (e.g. loss of mucilage ducts). Evidence has been
produced for a marked plasticity of form, which poses a number of
questions with regard to interspecific relationships. Evans (1964) has
reported on the chromosome numbers and condition in Laminaria
species.
Laminaria smhurinu. The results of a 4-year study on L. sacehrinu
in the British Isles were reported by Parke (1948). Gametophytes were
observed to be fertile throughout the year, but the young sporophytes
produced can be found in one of four types of habitat depending on the
season. Thus near low water mark, where the shore will be continually
covered by the sea, sporophytes are found throughout the year, continuous crops being produced by either protracted fruiting of the
gametophytes, or by continuous production of gametophytes. I n
intertidal habitats, where the shore is uncovered by the sea at low
water of spring tides, sporophyte production ceases during May and
June. In habitats several metres below E.L. W.S.T., sporophyte
development ceases between November and February due to a marked
reduction in light intensity. Sporophytes are not observed in habitats
A. D. BONEY
of Aswphyllum nodosum fronds similarly had a harmful effect, suggesting production by Aswphyllum of substances toxic to the Laminuria
sporelings.
9. Taxonomic observations on Laminaria species
More recent works on the taxonomy of Laminaria species have
tended to show overlapping of the specific characters of some entities.
Parke (1948) pointed out that growth forms of L. saccharina were
obtainable which could be fitted to the description of other distinct
species (e.g. L. hieroglyphiea, L. faroensis, L. longicruris). The need
was shown for more data on chromosome numbers, and for transplant
experiments. Sundene (1962) has shown how the forms of L. digitata
can be modified by environmental conditions. Burrows (1964) has
reviewed the more significant diagnostic characters of Laminuria
species, (e.g. shape of base of blade; blade texture and condition of
margin ; presence or absence of mucilage ducts), together with appearance of the meristoderm cells in surface view (Wilce, 1959). I n a
comparative study of European forms of L. saccharina cultured at
5°C and 10°C and of plants of similar forms from Nova Scotia which
failed to show all of the main characters of L. saccharina, the two forms
were found to be quite distinct in shape and size, even to size of cells
of the gametophytes. However, continued growth of plants of L.
saccharinu at the lower temperature resulted in marked differences in
its specific characters (e.g. loss of mucilage ducts). Evidence has been
produced for a marked plasticity of form, which poses a number of
questions with regard to interspecific relationships. Evans (1964) has
reported on the chromosome numbers and condition in Laminaria
species.
Laminaria smhurinu. The results of a 4-year study on L. sacehrinu
in the British Isles were reported by Parke (1948). Gametophytes were
observed to be fertile throughout the year, but the young sporophytes
produced can be found in one of four types of habitat depending on the
season. Thus near low water mark, where the shore will be continually
covered by the sea, sporophytes are found throughout the year, continuous crops being produced by either protracted fruiting of the
gametophytes, or by continuous production of gametophytes. I n
intertidal habitats, where the shore is uncovered by the sea at low
water of spring tides, sporophyte production ceases during May and
June. In habitats several metres below E.L. W.S.T., sporophyte
development ceases between November and February due to a marked
reduction in light intensity. Sporophytes are not observed in habitats