The lamina or blade in macroscopic algae like seaweed is a generally flattened structure that typically forms the principal bulk of the thallus. It is often developed into specialised organs such as flotation bladders and reproductive organs.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/80/Kelp._%2815272102411%29.jpg/220px-Kelp._%2815272102411%29.jpg)
The lamina is typically an expansion of the stipe which in term is attached to the substrate by the holdfast.