intraspecific hybridization of the wild-type strain(Py-WT, ♂) and the red-type pigmentation mutant(Py-HT, ♀) in was isolated from the recombinants. The gametophytic blades of the Py-WT strain have slow growth, thick blades, low major photosynthetic pigment content, and poor heat-resistance characters, while the gametophytic blades ofPy-HT have fast growth, thin blades, high major photosynthetic pigment content, and partial high-temperature resistance. After the conchospores of Py-WT and Py-HT strains were cultured at high temperature (24 for 13 days, the survival rates of the conchospores were 18.3% and 65.2%, respectively; however, the survival rate of HW-4conchospores at 24 was 77.5%. Furthermore, after the conchospores were cultured at high temperature (25HW-4 conchospores were 16.9%, 47.1% and 67.3%, respectively. The survival rate of the HW-4 conchospores at 24additionally, it was 4.0 times that of Py-WT and 1.4 times that of Py-HT. After the conchospore germlings from Py-WT, Py-HT and HW-4 strains(50-day-old, 19 for another 25 days, the mean blade length increased by 1.6, 1.6 and 3.3 times compared with the original lengths, respectively. The mean blade length of the HW-4 strain was 5.9 times that of Py-WT and 2.6 times that of Py-HT. After the 50-day-old conchospore germlings were cultured at 25HW-4 increased 1.3, 1.4 and 2.5 times, respectively, and the mean length of the blades of the HW-4 strain was 5.3 times that of Py-WT and 2.1 times that of Py-HT. In addition, the gametophytic blades of the parental strains began to curl and rot after 10–15 days in culture at high temperatures(24), and rotten seriously after 25 days. However, the HW-4 gametophytic blades curled a little after 25 days in culture at high temperatures, but did not rot even after 35 days. After the blades were cultured for another 15 days at 19was 76.0 mg/g, 111.1 mg/g and 132.3 mg/g, respectively, which was 3.1, 2.2 and 2.0 times that of Py-WT, respectively. The total was significantly higher than that of the parental blades. The numbers of conchospores released did not significantly differ among Py-WT, Py-HT and HW-4 strains. The above results show the following: (1) high-temperature resistance in HW-4 conchospores and F₁ gametophytic blades, and (2) improved growth rate and pigment content in HW-4 blades compared with the parental strains. Therefore, the improved strain (HW-4) is expected to be used for cultivation of