Crossing experiments in the non-digitate complex of Laminaria from both sides of the Atlantic

Laminaria longicruris from Nova Scotia and two forms of European L. saccharina have been successfully crossed in the laboratory. Parental and hybrid sporophytes were cultivated in the sea near Helgoland, where they reached maximum frond lengths of 40–120 cm. After 7 months all experimental plants were still non-sporogenous and were removed from the sea. Observations on genetically fixed traits and the problem of the relationships between non-digitate Laminaria forms from the eastern and western sides of the North Atlantic are discussed.