Alaria fistulosa, Druehlia fistulosa

Description: Thallus of this canopy-forming kelp is brown with a large branching holdfast (haptera), a stipe 25 cm (10 in) long, and a blade with midrib up to 25 m (82 ft) long and 1 m (3.2 ft) wide. The midrib is 2-3 cm (0.8-1.2 in) wide with gas-filled chambers (fistulae) that hold the blade in the water column. Reproductive sporophylls develop on the upper portion of the stipe. Habitat: This fast growing annual occurs on rock from the low intertidal to subtidal and forms offshore kelp beds in cold, semi-protected to exposed habitats.