Two plants of oarweed,Eklonia radiata (syn. Laminaria radiata),on the shore of the Southern Ocean in Victoria,Australia. The pictures shows the adhesive pads (yellow-green) known as holdfasts,that attach each plant to the rocky substrate. The thick trunk arising from each holdfast is called the stipe. Oarweeds,also known as kelp,are brown algae (Phaeophyta),typical of high energy coasts. The disc of the holdfast is flattened to produce a large area in contact with the rock in order to withstand wave action."Kelp" originally referred to the ash from burning brown seaweeds as part of the process for producing iodine. Brown seaweeds are also a source of mannitol and alginic acids,the latter being used in the dressing of fabrics,binders in paper manufacture,and the production of artificial leather. The pink organism encrusting the rock is a species of red alga,Lithophyllum |