Preliminary observations on the development of kelp gametophytes endophytic in red algae

The development of kelp gametophytes is described from field collections fr om the San Juan Islands, Washington from November, 1997 to March 1998. All gametophytes were endophytic in the cell walls of red algae, especially spe cies with filamentous or polysiphonous construction. Gametophyte density ra nged from a few to many hundreds of distinct individuals per host plant. Ga metophytes formed extensive vegetative growths of irregularly branching fil aments, mostly parallel to the host surface, consisting of up to 50 or more cells. Antheridia were formed at/or just above the surface of the host tha llus. The stalked egg apparatus was perpendicular to the host surface. Foll owing presumed fertilization, the zygotes developed with typical kelp embry ology to form small epiphytic blades. The specific identity of the gametoph ytes is unknown, although the host plants were collected from three sites w here the dominant kelp species were: a) Agarum fimbriatum, b) Nereocystis l uetkeana and c) Alaria marginata, Costaria costata and Laminaria groenlandi ca.