Male seaweed receptacle. Light micrograph of a section through a receptacle from male bladderwrack (Fucus Vesiculosus) brown algae, showing the conceptacles (round) containing the male reproductive organs (antheridia). The interior of the conceptacles is lined with hairs (paraphyses), the tips of which bear the antheridia. These male reproductive structures are released through the ostiole (hole at top of conceptacle) to the sea, where they are chemotactically attracted to the conceptacles of female seaweeds to fertilise the ova (female reproductive cells). Magnification: x5 when printed 10 centimetres wide.