173
the most transparent lakes in Europe. It has a
Secchi disc transparency up to 23 m on some
occasions. Study of a profi le across the vegetation of the muddy part of the littoral zone had
shown from the shore lakeward successively
Phragmites australis, Typha angustifolia, Najas
marina, Potamogeton perfoliatus , etc.
Interestingly, in Lake Titicaca , situated at an
altitude of 3,815 m, Potamogeton strictes may
descend to a depth of little >11 m. This is, perhaps, the most reliable depth up to which an
angiosperm may reach. In the same lake, Chara
and Hygrohypnum may reach up to a depth of 14
and 29 m, respectively (Tutin 1940 ).
However, Pearsall ( 1921 ), on the basics of
his works on English Lakes, had suggested that
the main factor(s), which may determine the differences in vegetation within the broad limits of
depth and fl ux, is the physico-chemical nature
of the sediment. Further, Misra ( 1938 ) had
worked on the substrata required by various
submerged plants in the English Lakes in detail.
He had concluded that the mud optional for
P. perfoliatus is a mixture of organic material
and silt, with a minimum C–N ratio, a high
capacity to produce NH 3 and a low redox potential. This suggests much bacterial activity and a
high content of exchangeable cations. Mishra,
further, following Pearsall, opined that the more
highly organic mass are formed by too rapid
sedimentation to permit growth of the plant that
seemingly might not be able to raise itself in the
mud as the latter accumulates.
8.5.7 AM of Lakes Mendota,
Wisconsin and Green
of the USA
These lakes were studied by some workers
(Rickett 1922 , 1924 ; Lind and Cottam 1969 ).
There used to be an almost continuous girdle
of submerged AM extending to 5–5.5 m.
Emergent and fl oating AM were few. Some of
the abundant AM are Nymphaea odorata,
Lemna minor, Wolffi a columbiana , etc. Green
Lake was said to be more transparent than Lake
Mendota.
8.5.8 AM of Lake Victoria
The emergent and fl oating-leafed AM of some
parts of the shores of the Lake Victoria had been
well described by Eggerling ( 1935 ) and Carter
( 1955 ). In Lake Victoria, where the slope of the
basin is very gentle, the prevalent terrestrial
grassland generally passes into a grass swamp,
which is usually eulittoral. Within this, usually
there is a Papyrus swamp. It is ordinarily dominated by Cyperus papyrus, Dryopteris atrata,
etc. The Papyrus, except in very shallow water,
has a layer of interwoven roots forming a mat
which generally lies well above the bottom. The
submerged vegetation could include Potamogeton
schweinfurthii in water up to a depth of 6 m
(Spence 1967b ).
8.5.9 AM of Lake Tanganyika
Van Meel ( 1952 ) had given a general account of
the vegetation of the basin. But only few details
had been given about submerged AM. However,
the latter is not greatly developed and consists
mainly of P. pectinatus, Najas horrida, Vallisneria
sp., etc.
8.5.10 AM of the Lakes of New
Zealand (NZ)
The native aquatic fl ora seems to be very restricted
in NZ. As such, there had not been much reports
on the AM of a single typical lake in New Zealand.
It appears that certain species, notably, Potamogeton cheesemanii and Myriophyllum propinquum , are very plastic. Their ecophenes may
occupy a number of niches, which, with a greater
fl ora, would, probably, be fi lled by different
species. Nevertheless, Mason ( 1969 ) had given a
general account of the AM of the Canterbury
district of South Island. Some of the abundant AM
in clear permanent waters of lakes, with little or no
silting, are Isoetes alpines, Limosella lineata , etc.
Elodea canadensis is said to go deeper than any
native plant. Potamogeton cheesemanii is dominant where silting occurs. Some of NZ species are
8.5 AM of Certain Lakes of the World
the most transparent lakes in Europe. It has a
Secchi disc transparency up to 23 m on some
occasions. Study of a profi le across the vegetation of the muddy part of the littoral zone had
shown from the shore lakeward successively
Phragmites australis, Typha angustifolia, Najas
marina, Potamogeton perfoliatus , etc.
Interestingly, in Lake Titicaca , situated at an
altitude of 3,815 m, Potamogeton strictes may
descend to a depth of little >11 m. This is, perhaps, the most reliable depth up to which an
angiosperm may reach. In the same lake, Chara
and Hygrohypnum may reach up to a depth of 14
and 29 m, respectively (Tutin 1940 ).
However, Pearsall ( 1921 ), on the basics of
his works on English Lakes, had suggested that
the main factor(s), which may determine the differences in vegetation within the broad limits of
depth and fl ux, is the physico-chemical nature
of the sediment. Further, Misra ( 1938 ) had
worked on the substrata required by various
submerged plants in the English Lakes in detail.
He had concluded that the mud optional for
P. perfoliatus is a mixture of organic material
and silt, with a minimum C–N ratio, a high
capacity to produce NH 3 and a low redox potential. This suggests much bacterial activity and a
high content of exchangeable cations. Mishra,
further, following Pearsall, opined that the more
highly organic mass are formed by too rapid
sedimentation to permit growth of the plant that
seemingly might not be able to raise itself in the
mud as the latter accumulates.
8.5.7 AM of Lakes Mendota,
Wisconsin and Green
of the USA
These lakes were studied by some workers
(Rickett 1922 , 1924 ; Lind and Cottam 1969 ).
There used to be an almost continuous girdle
of submerged AM extending to 5–5.5 m.
Emergent and fl oating AM were few. Some of
the abundant AM are Nymphaea odorata,
Lemna minor, Wolffi a columbiana , etc. Green
Lake was said to be more transparent than Lake
Mendota.
8.5.8 AM of Lake Victoria
The emergent and fl oating-leafed AM of some
parts of the shores of the Lake Victoria had been
well described by Eggerling ( 1935 ) and Carter
( 1955 ). In Lake Victoria, where the slope of the
basin is very gentle, the prevalent terrestrial
grassland generally passes into a grass swamp,
which is usually eulittoral. Within this, usually
there is a Papyrus swamp. It is ordinarily dominated by Cyperus papyrus, Dryopteris atrata,
etc. The Papyrus, except in very shallow water,
has a layer of interwoven roots forming a mat
which generally lies well above the bottom. The
submerged vegetation could include Potamogeton
schweinfurthii in water up to a depth of 6 m
(Spence 1967b ).
8.5.9 AM of Lake Tanganyika
Van Meel ( 1952 ) had given a general account of
the vegetation of the basin. But only few details
had been given about submerged AM. However,
the latter is not greatly developed and consists
mainly of P. pectinatus, Najas horrida, Vallisneria
sp., etc.
8.5.10 AM of the Lakes of New
Zealand (NZ)
The native aquatic fl ora seems to be very restricted
in NZ. As such, there had not been much reports
on the AM of a single typical lake in New Zealand.
It appears that certain species, notably, Potamogeton cheesemanii and Myriophyllum propinquum , are very plastic. Their ecophenes may
occupy a number of niches, which, with a greater
fl ora, would, probably, be fi lled by different
species. Nevertheless, Mason ( 1969 ) had given a
general account of the AM of the Canterbury
district of South Island. Some of the abundant AM
in clear permanent waters of lakes, with little or no
silting, are Isoetes alpines, Limosella lineata , etc.
Elodea canadensis is said to go deeper than any
native plant. Potamogeton cheesemanii is dominant where silting occurs. Some of NZ species are
8.5 AM of Certain Lakes of the World