Family Description:
These are all very finely branched red seaweeds. Plants are often uniseriate (monosiphonous) filaments, which are corticated by small cells or rhizoids in some species. These filaments are the main axis of the plant. Branching is opposite, alternate, or verticillate (with branches arranged in whorls around the axis). Many branches have determinate growth, and are usually called branchlets, but a few continue to grow to produce new axes like the one bearing them (these continue to be called branches). Tetrasporangia are cruciately or tetrahedrally divided. In some cases, bisporangia (sporangia containing two spores) or polysporangia (sporangia containing many spores) are borne in place of tetrasporangia. Cystocarps are naked or at most surrounded by involucral filaments. Most plants in this family are quite small and require a microscope or very good hand lens to see these diagnostic features.

Species description:
This is one of the coarser members of this family of red algae, and it is usually purplish brown to reddish brown in color. It is perennial and so extremely densely branched that it appears woolly.

The main axes are up to 40 cm (16 in) tall, but most individuals that you find will be much smaller, usually no more than 5 to 10 cm (2 to 4 in) high. Each cylindrical axis is up to 2 mm in diameter. The first (main axis) to third orders of branches are corticated; that is, they have a think, barklike covering that will be apparent when you examine them through a microscope. The lateral branches are up to 5 cm (2 in) long and are spaced well apart from each other, but the tertiary and higher orders of branching are extremely crowded. The lateral branches come off the main axis in a rather alternate fashion. The branchlets are somewhat curled and have slender, pointed tips. At the base of Beauty Bush the holdfast is either discoidal or is composed of rhizoids that sprout from basal cells.

Tetrasporangia occur only on the upper sides of the ultimate branchlets; they are sessile (lack stalks) and almost spherical.

Source:  North Pacific Seaweeds

Synonyms and Alternate Names:
Callithamnion arborescens
Callithamnion pikeanum var. pacificum
Callithamnion pikeanum var. pikeanum