Green algae. Hair-like green algae (Chlorophyta) clinging to rocks. These algae inhabit an intertidal zone, where a river's freshwater mixes with the saltwater of a loch. Seaweed (upper left) are also seen. Green algae are adapted to exploit a habitat that is rich in nutrients and sunlight, but are subjected to severe environmental stresses. These stresses include constantly changing salinity and temperature, occasional drying out, and bashing by waves. Algae are primitive plants that have no true leaves, stems, roots, flowers or veins. Like higher plants they can photosynthesise (grow using the Sun's energy). Photographed in north-western Scotland.