Drainage basin: The area drained by a river and its tributaries. A drainage basin is considered to be an open system because water can be added or lost from a drainage basin. Source: The beginning of a river. A river may have multiple sources.
Milk thistle (Silybum marianum) is a thorny plant presenting decorative leaves with a white pattern of veins and purple flower heads. The plant originates from mountains of the Mediterranean region, where it forms scrub on a rocky base.
Leaves: The leaves of the milk thistle are oblong to lanceolate in shape. They are either lobate or pinnate, with spiny edges. Leaves are hairless, are alternate, and have milky-white veins. The upper leaves clasp the stem. Height: Milk thistle grows up to one metre tall.