The sporophyll is formed like an undulate wing at both side of the stipe when leaf of Undaria pinnatifida Suringar developes to 50cm in length. The sorus is formed at this region，and on the condition that temperature of water is about 14℃，the zoospores are liberated into the water.
Recently it is said that the polysaccharides which is included in sporophyll is effective to biological activities，though the chemical components and fine structure of the sporophyII are not
known. In this experiment，the development and differentiation of fresh Undaria pinnatifida Suringar were studied by means of transparent electron microscope. The results revealed that the paraphysis is formed from developing epidermal cell. In the cytoplasm of paraphysis，there are a
nucleus，nucleolus，several chloroplasts and many mitochondria. The Golgi body consist of well developed Golgi lamellae and vesicles. Many secreting vesicles are observed at the end of Golgi lamellae. The mucilage caps are stained pinkishe by toluidine blue indicating to contain many
mucoids. The zoosporangial cell possess many nucleus，chloroplasts，Golgi bodies and many vesicles arround mitochondria and nucleus. Some dense and osmiophilic bodies，which are suggestive of fucosan vesicles，a reobserved apical parts of paraphysis，basal cell and cortical cells. Many mucilaginous substances，which are stained violet-pinkishe by toluidine blue and are suggested to contain many polysaccharides，are observed in the cell wall，in tercellular spaces and mucilage caps.