Contrary to popular opinion, there is nothing exclusively Japanese, or even particularly Asian about eating seaweeds. Seaweed dishes are featured in the culinary traditions of many western countries, from Welsh laverbread & delicate Irish carragheen puddings to savory Icelandic fish dishes, seasoned with tangy dulse. Now, ranges of dried sea vegetables are widely available from supermarkets & health food stores. Seaweeds are an excellent source of vitamins & minerals, & have exciting textures & tastes. Here is a cook's guide to seaweeds & sea vegetables as an introduction to an exciting collection of recipes, both new & traditional -- try Spicy Chicken & Hijiki Pancakes, Wakame-wrapped Sardines or Savory Rice with Arame. Illus.