Family Description:
Most members of this family are flattened blades; they can have single, entire blades or be much-branched. The blades can be smooth or covered with short protuberances called papillae. Like other red algae, the characters that unite this family are details of the female reproductive apparatus and post-fertilization development. Tetrasporangia are cruciate and occur in internal sori.
Although members of this family have an alternation of isomorphic generations, the two generations have different cell wall carbohydrates. When extracted, the carbohydrates of the gametophyte form a gel whereas those of the tetrasporophyte form a viscous liquid. These carbohydrates represent two different forms of carrageenan, an additive to most ice creams to keep them smooth, and to chocolate milk to keep the chocolate in suspension.

Species description:
The thin, encrusting holdfast is usually perennial and supports crowded clusters of thick, erect blades in spring and early summer. The blades are rounded at their tops but often shallowly cleft into two or three lobes; they are also widest above the middle and have a furrowed upper stipe-lower blade. Most specimens reach just 4 cm (1.6 in) tall and 2 cm (0.8 in) wide, but sometimes you can find larger specimens. Their color is olive green to dark purple.

Like other species of Mazzaella, the Iridescent Horn-of-plenty has cystocarps that bulge like large pimples from the surfaces of the blades.

This species is more abundant in exposed locations, where it grows on rocks.

In the high intertidal zone at Barkley Sound on the west coast of Vancouver Island, British Columbia, researchers have found that the blades of the Iridescent Horn-of-plenty do not thin themselves even when they are very crowded. Usually, when individual algae of the same age and species are growing in crowded conditions, the smallest ones die, which results in self-thinning. These workers refer to this species as a "clonal" alga because each thallus has many blades, each of which could potentially survive on its own. Other examples of clonal species are found in Mastocarpus and Gracilaria.

Source:  North Pacific Seaweeds

Synonyms and Alternate Names:
Mazzaella cornucopiae