Complex sentence: In these explorations he collected and classified about 6000 plants which were until then mostly unknown in Europe, which he afterwards described in "Plantes equinoxiales" (Paris, 1808-1816).
Split into simpler sentences: In these explorations he collected and classified about 6000 plants which were until then mostly unknown in Europe. He later described his finds in "Plantes equinoxiales" (Paris, 1808-1816).