এগুলির কাঠামো বাহ্যত কান্ড ও পাতার মতো এগুলিতে আরও আছে বায়ুস্থলী ও মজবুত ধারক ###>Kelps are brown algae which comprise the largest seaweeds viz Macrocystis and Nereocystis they have structures which superficially resemble leaves and stems also large air filled bladders and strong holdfasts