Hormosira banksii

Neptune's necklace, Hormosira banksii, also known as sea grapes or bubbleweed, is a species of seaweed found in Australia and New Zealand. It is a common seaweed found in rock pools at mid-tide levels and is characterised by strings of olive-brown hollow beads. The beads have a slimy layer which keeps the moisture locked up inside. They also store gas, allowing them to stand up in water. This also allows them to obtain more sunlight and to move with the flow of the current. Each bead is a knobbly bladder filled with water that prevents desiccation between tides.

The unattached form of this seaweed (commonly found in mangroves) reproduce asexually, from broken fragments. The attached form of the seaweed reproduce sexually. Their sex organs are the pimple like features found on the surface of the beads. At high tide plant squeezes out their clusters of eggs or sperm in sticky masses. All plants release at the same time, maximizing fertilisation.

They are mostly found in the mid-tide zone (littoral zone) or in rock pools, where they receive much light and enough sea water to avoid desiccation. One of their behavioural adaptations is living in groups, preventing moisture loss and drying out.

The plants, especially when young, are edible.