Porphyra pseudolinearis and P. dentata from Korea were crossed and the hybrid was cultured at different temperatures (5, 10, 15, 20 or $25^{circ}C$), photon flux densities (10, 20, 40 or 80${mu}$mol m$^{-2}$s$^{-1}$) under photoperiods (14L:10D and 10L:14D). In the hybrids, the conchocelis grew faster at 2$0^{circ}C$ and 40$mu$mol m$^{-2}$ s$^{-1}$ at $25^{circ}C$ only, and were abundant, when cultured under 10L:14D. Foliose thalli of the hybrid grew rapidly at conditions of 10-2$0^{circ}C$, 10L:14D and 15-2$0^{circ}C$, 14L:10D but slowly at 5 and 2$0^{circ}C$. No archeospores were observed any tested culture condition. Spermatangial and zygotosporangial sori were formed at the marginal portion o mature thallus. Zygotospores from the hybrid were released at 10-2$0^{circ}C$ under both photoperiods, and gave rise to form conchocelis filament. Monoecious thalli were observed at 1$0^{circ}C$ under 14L:10D. Neither monospores nor protothalli were produced from the conchocelis in culture.