Abstract: The causes threatening Pellacalyx yunnanensis Hu, a species endemic to Yunnan and a tree receiving priority protection in China, are discussed. The study focuses on its seed anatomy, the relations between different methods of seed storage and seed germination, and the effects of seed moisture content, tem-perature and ligh density on seed germination. It is concluded that the main causes of species decline involve the facts that seeds ripen during the dry season, short life-span prevents seeds from surviving until the rainy season, and most fail to germinate. Seeds require high temperatures and abundant moisture to germinate successfully. Reasons for the. species decline include long-term natural factors, such as climatic and geological changes, and human-related activity, particularly defo-restation. Thus, some measures for effectively preserving this species are proposed.

Key words: Rare plants