Chylocladia Clavellosa

When Anna Atkins made her cyanotype of this pinkish-red seaweed, it was known as Chylocladia clavellosa. Today, it is referred to as Lomentaria clavellosa, or more commonly, "feathery tube weed". It wouldn't have been difficult for Atkins to find: the plant is widespread around Britain and Ireland, and can be spotted many other places around western Europe. 

Atkins created her cyanotype photograms by placing the specimen onto light-sensitive paper, and then exposing paper and subject to the sun for a period of time. She then developed the image using the cyanotype process, resulting in a rich blue background.