Physiological studies on the hybrid by crossing between two dioecious species, Porphyra pseudolinearis and P. dentata from Korea were conducted at constant temperatures (5, 10, 15, 20, and $25^{circ}C$), at photon flux densities (10, 20, 40, and $80;{mu}mol;m^{-2}s^{-1}$) under photoperiods (14 L : 10 D and 10 L : 14 D). In the hybrid, higher growth of conchocelis was observed at 20 and $40;{mu}mol;m^{-2}s^{-1}$ under 14 L : 10 D. Conchosporangial branches were produced under $10-80;{mu}mol;m^{-2}s^{-1}$ at only $25^{circ}C$, and were abundant when the conchocelis was cultured under 10 L : 14 D. Foliose thalli of the hybrid grew well at the conditions of $10-20^{circ}C$, 10 L : 14 D and $15-20^{circ}C$, 14 L : 10 D. The foliose thalli grew very slowly at $5^{circ}C$ and $30^{circ}C$, respectively. No archeospores were observed at any culture conditions. Spermatangial and zygotosporangial sori were formed at the marginal portion of mature thallus. Zygotospores from the hybrid were released at $10-2^{circ}C$ under both photoperiods, and gave rise to form conchocelis filament. Monoecious thalli were observed at $10^{circ}C$ under 14 L : 10 D. Neither monospores nor protothalli were produced from the conchocelis in culture.