||Although the two lakes are basically considered oligotrophic (Koussouris, 1978 and Overbeck et al., 1982) the vascular plants found there (Myriophyllum spicatum, Potamogeton pectinatus, Ranunculus trichophyllus, etc.) mostly occur in eutrophic or mesotrophic lakes (Koumpli-Sovantzi, 1983). From a florisrtic point of view, they have been investigated mainly by Koumpli-Sovantzi (1983). Lake Trichonida is surrounded by cultivated fields with Nicotiana tabaccum, Citrus and olive trees. At the littoral zone of the lake herbs predominate while shrubs (Vitex agnus-castus, Nerium oleander, Rubus sanctus) and trees (Platanus orientalis. Salix alba, Populus alba) occur only sporadically. At the upper infralittoral zone Phragmites australis and Typha domingensis dominate and there shape an almost continuous zone on the alluvial deposits mainly at the western part of the lake. Iris pseudacorus participates in low frequency of occurence in the structure of the plant communities of the upper infralittoral zone.This zone is interrupted, in some places only, by human activities. The middle infralittoral zone is locally covered by Nymphaea alba and Potamogeton nodosus species, while at the lower infralittoral zone, species of the genera Potamogeton, Myriophyllum and Chara (Charophyta) predominate. The plankton occuring in this site are of special importance, because they are the dominant element of the primary flora, and are valuable indicators of the biological state of the lakes. Phytoplankton consists of numerous species of algae (Cyanophyta, Pyrrhophyta, Chlorophyta, Charophyta, Chrysophyta, Bacillariophyta, Xanthophyta and Cryptophyta) (Tafas, 1991) and contains cosmopolitan species accompanied by some endemic taxa as well as some of tropical origin. In the north-east and south-east sides of lake Trichonida, rocky calcareous places with shrubby vegetation are observed. Lake Lysimachia is surrounded by alluvial deposits, where cultivated fields mainly with Nicotiana tabbacum exist. In several places permanent or seasonal marshes occur. A macrovegetational study of the aquatic tracheophytes was carried out by Koumpli-Sovatzi & Vallianatou (1985). The natural shoreline vegetation particularly consists of herbs (Scirpus holoschoenus, Paspalum paspaloides, Mentha aquatica, Kickxia elatine, Cyperus longus, Carex otrubae, Juncus acutus etc.). Some shrubs (Vitex agnus-castus) and trees (Platanus orientalis, Salix alba, Populus alba) have scattered distributions. The species dominating near the shore line is Phragmites australis. It forms an extremely dense, almost continuous reed-fringe, mainly near the waters edge, as well as in the upper infralittoral zone and is interrupted in several places only, by human activities. The greatest characteristic cover is presented by the species Paspalum paspaloides. The submerged species Vallisneria spiralis predominates in the lower infralittoral zone, forming dense stands, while Ceratophyllum demersum, Myriophyllum spicatum and Najas marina present the lower cover.