59 / 90
1963). The occurrence of the species in draining canals along the Danube
River (Ко ч е в , Й о р д а н о в , 1981) is reported, but no materials in the
Bulgarian herbaria are preserved. None of the indicated localities have been
confirmed in the recent years despite the special field research. Indications for
the extinction of the species are changes in the water regime, termination of
rice production etc. The species occurs as a dominant in the fish nursery over
an area of 0.50 ha. The community is formed by the following species:
Marsilea
quadrifolia
L.,
Potamogeton fluitans
Roch. and single specimens of
Lemna
minor
L.,
Typha latifolia
L. and
Schoenoplectus lacustris
(L.) Palla. The water
depth is - 0.5 m, water is relatively pure. The locality is large and the
population is relatively stable. In this locality
Marsilea quadrifolia
is conserved
in a draining canal. Such canals exist in many places in Bulgaria but this plant
does not occur there. In this case the question arises - why, despite the
abundance of appropriate habitats, the species is not present? There are two
possible answers, for which special research is needed:
1. Primary rareness of the species in Bulgaria and on the Balkans.
2. Unknown reasons, probably related to some peculiarities of its growth
and reproduction.
6540.26390.
POTAMOGETON TRICHOIDES
CHAM. ET
S C H L E C H T . - LJ-43; SC (R. TZ.), SO-99531
Middle Danube Plain, the „Murtvoto blato“ Marsh on the Persina Island,
with fruits, 06. 1998.
The population is numerous but isolated. This rare species is known from
a single locality in the Danube Plain (Kozlodui Marsh and Svishtov Marsh)
and Thracian Plain (Пе не в , 1984). After the destruction of the marshes
along the Danubian coast near Kozlodui and Svishtov, the species has been
considered extinct in Northern Bulgaria.
4600.19710.
LEMNA GIBBA
L. - LJ-31, LJ-22, SC
(R.TZ.) SOM-158878
Middle Danube Plain, in a drainage canal in the locality ,,Gerena“, near
the village of Obnova, 27.06.2003.
The second locality is ,,Blatoto“, village of Debovo, along the Osam River,
June of 2000. The only previously known locality for the Danube Plain was
near the town of Lorn ( Ко ч е в , 1984). The existence of this rare species in
other parts of the Middle Danube Plain is possible.
60
Электронная Научная СельскоХозяйственная Библиотека