stalked kelp

Pterygophora californica is a large brown seaweed and may grow to about three metres in height. It is attached to a rocky substrate by its holdfast and has a single, tough, woody stipe or stem up to two metres long and 2 cm (0.8 in) in diameter. It is a long-lived perennial algae which may survive for twenty-five years, and annual growth rings can be seen in the stipe. There are a number of smooth blades arranged on either side of the top half of the stipe. These are sporophylls and bear reproductive organs called sporangia in which the spores are formed. The terminal blade is linear, has a midrib and is larger than the others, growing up to 90 cm (33 in) long.

Pterygophora californica is found in the sublittoral zone of the west coast of North America from Vancouver Island, British Columbia south to Bahía Rosario, Baja California, Mexico at depths down to about ten metres.

Pterygophora californica grows in underwater kelp forests with other brown algae including the annual bull kelp (Nereocystis luetkeana) and the perennial giant kelp (Macrocystis pyrifera). It is a dominant understory kelp species in these kelp forests, and creates a sub-surface canopy. Brown seaweeds are photosynthetic organisms and their growth is mainly restricted by the availability of light. P. californica can be restricted in its growth by shading from bull and giant kelp canopies. Various algae try to get a head start by attaching themselves to P. californica well above the ocean floor; this strategy is known as epiphyty. These include red algae (Rhodophyte spp.), bull kelp (Nereocystis luetkeana), and sea belt (Saccharina latissima). The most common cause of death of P. californica is being torn from the rocks during storms, which is made more likely by the increased drag caused by the burden from epiphytes. P. californica and other Laminariales attempt to reduce their epiphytic load by periodically sloughing off their surface layers and by the production of "antifouling" substances such as phenols in their tissues. …