OBSERVATIONS ON THE ECOLOGY OF LAMINARIA SINCLAIRII ON THREE NORTHERN OREGON BEACHES1,2

Laminaria sinclairii (Harvey) Furlow, Anderson and Eaton occurs only on the Pacific Coast, of North America and is usually restricted to rocks on beaches subjected, to moderate to heavy surf and a large seasonal fluctuation in sand level. It was observed and measured over a 2-year period-on 3 such beaches in northern Oregon. Growth, rate and, relative dominance are greatest in the lowest and most exposed parts of the inter tidal zone, where surf action and sand burial are greatest. The sand level begins to build up on the beach in April and continues to rise, burying the plants, throughout the summer, until the first, heavy storms in fall again remove the sand. Maximum growth occurs in early summer, prior to burial. The blades are lost in December and regenerated in January. Ripe sori are produced on the old blades just before they are lost and on the new blades just after they appear. The gametophyles which, develop from spores produced by these sori apparently do not usually produce sporophytes. In March and April there is considerable production of new stipes and blades from the haptera at the margins of the holdfast and this is apparently the chief means of reproduction.