Sentence:  In addition to gas bladders, the thallus of reproductive rockweed, "Fucus", has inflated tips called <WSD>receptacles</WSD>. The small bumps on the surface of each <WSD>receptacle</WSD> are conceptacles, chambers within which the gametangia grow. 
Meaning of the word marked with <WSD> tags:  A structure at the end of a branch of an alga containing conceptacles (reproductive organs).