Nasturtium species - Water-cress
This is widespread in streams in Lanarkshire. There are two species and a hybrid. The species can only be differentiated in the field when there mature fruits.
Nasturtium officinale has shorter thickers fruits with two rows of seeds.
Nasturtium microphyllum has longer thinner fruits with the seeds mainly in one row.
Nasturtium x. sterilis is the sterile hybrid and can be identified in the field as the flowers have much less pollen and the fruits are shorter, misshapen with few if any seeds.
Garden Nasturtium belongs to another family.