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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.
Turkish Towel usually forms a single, erect blade up to 50 cm (20 in) or more tall and about 20 cm (8 in) wide. It grows best in somewhat exposed locations, where the blade is rather thick and even somewhat stiff, but it also occurs in more protected waters where it tends to be thinner. In either case, the blade is rather irregular in outline although it tends to narrow at the top.
The most distinctive feature of this species is that both sides of the blade are covered with a carpet of small outgrowths, giving the whole blade the rather fanciful appearance of a thick bath towel. Theseoutgrowths, which are called papillae, are associated with reproductive structures. The main blade can tatter and acquire holes with age, and can shrink and darken as well. When young, it is dark red to rich purple in color, and is iridescent when wet.
Basally, the main blade tapers to a short stipe, which can also carry a few additional blades that are much smaller in size (less than 1 cm or less than 0.4 in tall). The holdfast at the lower end of the stipe is small and discoidal.
This species can be a conspicuous member of the low intertidal-upper subtidal seaweed community in the southern area covered by this book, but it becomes much less conspicuous in the northern part of its range.
Source: North Pacific Seaweeds