Hen pen is an exceptionally pretty, feathery-shaped branched green seaweed. It is mostly bright green in color and remarkably flexible. The 'leaf' (thallus) consists of a single cell containing lots of cell nuclei without partitions. This seaweed is fairly common in the delta region, but is rare in the wadden region, only found at the foot of dikes or on pontoons. Hen pen is grazed upon by many marine organisms.