Abstract: Carpospore-germlings of the marine alga Gracilariopsis sjostedtii (Kylin) Dawson cultured at different temperatures in enriched sea water showed a maximum rate of growth at 25 ℃. In addition, the germlings demonstrated a marked ability to withstand temperature as high as 35 ℃. This distinct behaviour indicates that the sporelings of this species play an important role in with standing the high-temperature months in the biennial cycle of vegetative growth. Ecological observations confirm our assumption. According to our survey data, plantlets about 1 cm in height do exist in the natural habitat at Zhanjiang from July. to September when the larger thalli are completely damaged. The most luxurious population of the sporelings appeared in April, May and June with an apparent diminution in the hottest months (from July through September). At that time of the year, the vegetative growth almost entirely stopped. These dormancy-like plantlets, however, grew anew and formed the plantlets of October and early November as the water temperature declines. They grew vigorously throughout the winter and attained the tallest growth in the following spring.Cutting experiments for the wild plant have been carried out in the field. The average growth rate obtained for the generative thalli was found to be 0.6 cm per day.