Receptacles occur at the ends of axes of algae such as Fucus .
Sterile hairs, paraphyses, are also anchored to the conceptacle wall and extend out of the opening of the conceptacle on the receptacle surface. Kelp are able to grow so large because of several specialized structures that have developed. The thallus of the kelp has different cell layers, and each has a specialized function. The cortex and epidermis are made up of pigmented cells where photosynthesis occurs, allowing the kelp to provide itself with nutrition. This allows the holdfast and lower portions of the stipe to get nutrition at the bottom of the ocean floor where there is little sunlight.