Abstract: So far, only one species of Porphyra, namely P. tenera Kjellm., has been reported from the vast Po-hal and Huang-hai regions In the course of our work on the life history of Porphyra tenera, we have found that in the small region of Tsingtao alone, there are represented at least 5 or even 6 species of Porphyra and among them some are as yet undescribed. In the present report, one of these new species will be described. Description of the new species: Porphyra marginata Tseng et T. J. Chang, sp. nov. Thalli generally 12–24 cm, sometimes reaching 40 cm in height, light or yellowish brownish-purple, with shortly stiped blade arising from a discoid holdfast; the blades orbiculate or suborbiculate, perforated, with cordate or umbilicate base and undulate to much folded marginal portions, membranaceous, monostromatic, to 38 μ thick; vegetative cells squarish or subrectangular with roundish corner in surface view, and subrectangular, 10–15 μ, sometimes 20 μ broad, about twice as high as broad in sectional view, with a single yellowish to light purplish, axial, stellate chromatophore; marginal portion of the blade consisting of 5–10, sometimes more, rows of degenerated cells; plants homothallic; spermatangia forming a more or less continuous region just inside of the degenerated marginal portion and also patches of irregular shape in the inner portion of the blade, composed of 64 spermatia arranged according to the following mode of division: ♂ A2B4C8; sporocarps dispersed in the part of the blade inside of the degenerated margin, composed of 16 carpospores arranged according to the following mode of division: ♀ A2B2C4, and intermixed with vegetative cells or degenerated unfertilized carpogonia. The type specimen, MB 54-493, was collected from near lower littoral rocks at wharf No. 6, Chungkang, Tsingtao on 15, Ⅳ, 1954 and deposited in the Herbarium of the Institute of Marine Biology, Academia Sinica. The species is widely distributed in the Tsingtao region and besides Chungkang in the Kiauchow Bay, has also been collected many times from the following places outside the Kiauchow Bay: Ta-he-lan and Siao-he-lan, Tuantao Bay; Lushun Park, Hueichuan Bay; Taiping Bay and Shih-lao-jen. Besides, this species was also collected once from Chengshantao (Cape Shantung), Yungcheng District. The growing season of the present species is very long, from late December to May of the next year, but its most luxuriant growth season is from February to April. The thalli are brownish, yellowish purple when living, turning to light purple upon drying. Specimens tend to crack upon excessive drying. Vegetative characteristics: Porphyra marginata is principally characterized by the blade margin with several rows of degenerated cells. When the thalli are very small, there is no difference between the marginal cells and those inside. When the thalli reach about 1.5–2.0 cm broad, the marginal cells gradually degenerate; first the cells stop growing in size, then the chromatophores keep on loosing their original yellowish purple color, then the cells turn pale yellowish and finally become colorless. The small colorless marginal cells conspicuously contrast with the inner cells which are of rich yellowish purple color and of normal size. At first, there may be only two to four rows of such degenerated cells at the margin; with the growth in size of the thalli, the number of rows of degenerated cells gradually increases to 10 or even more. Owing to the pressure from growth and division of ordinary vegetative cells next to the degenerated cells, the latter will eventually be dropped off. Concurrently, however, new degenerated cells keep on being formed from normal cells within, until those next to the degenerated marginal cells become involved in sexual reproduction. It is of interest to note that in this species, very frequent growths of the colonial Licmorphora on the blade edge offer a great help in the quick determination of the species. Degeneration phenomenon is not limited to the marginal cells of the blade; it also exists in the cells fringing the perforations of the blade caused by mechanical injury or animal biting. These cells, like those of the marginal portion of the blade, gradually become smaller and paler, conspicuously different from the ordinary purplish cells elsewhere. Therefore, it may be said that degeneration of cells is characteristic of all fringing cells, at the blade margin as well as along the edge of the perforation. So far, this unique growth phenomenon is known only in the present species and serves to differentiate it from all other known species of Porphyra. When the thalli are sexually mature, the cells next to the degenerated marginal cells undergo metamorphosis and change into sexual cells. With the dropping off of the marginal cells, marginal characteristic will no longer be detectable in the fertile portions of the blades. However, in the suprabasal region where the cells are comparatively young and not yet sexually mature, the marginal characteristic can be easily detected. Owing to the active growth of the cells just inside the degenerated marginal portion, the latter often becomes split into lobes . The exceptionally strong meristematic activity of the suprabasal region is also characteristic of Porphyra marginata; when young, the base of the blade is generally cordate or umbilicate, with the further growth of the thalli, owing to the comparatively stronger meristematic activity of the suprabasal part of the thalli, it may form a very complicated system with this part of the blade folding back and forth in a subspiral manner. When thalli with strongly developed suprabasal parts of the blades are made into herbarium specimens, it appears as if two or three or even more thalli of different ages pressed together in the same piece of herbarium paper with the younger ones on top of the older ones. Degree of the complication of the repeatedly folding system, however, differs with the ecological conditions. In places such as Taiping Bay, where the thalli are exposed to strong surf, the folding system of their suprabasal parts is relatively simple, while in places such as Chungkang where the thalli grow on sheltered rocks, it is very complicated.