Abstract: The floral development of a critically endangered plant Euryodendron excelsum from Ternstroemioideae (Theaceae) has been observed under scanning electron microscope (SEM) for the first time . The flower of E. excelsum is bisexual and teleianthous . Five sepal primordia are initiated 2􊄯5 spirally and arranged in one whorl when mature , and so are petals. Sepals and petals are initiated in the same order either clockwise or counterclockwise in the same flower . The androecial part is a ring primordium in the beginning . The first five stamen primordia are initiated on this ring primordium at antisepalous positions and then other stamen primordia appear on two sides of each of the first five primordia . Finally a total of 25 stamen primordia are initiated from the ring primordium and arranged in one whorl but could be grouped into 5 fascicles. Three sequentially initiated carpels compose an ovary which has an axile- central placenta with three locules and a truncate
and indehiscent stigma . The floral development of E. excelsum is distinctly different from plants in Theoideae .

Key words: Theaceae

摘要： 利用扫描电镜首次观察了山茶科极濒危植物猪血木( Euryodendron excelsum) 的花器官发生过程。猪血木的花为两性完全花, 萼片和花瓣均为2􊄯5 螺旋向心发生, 单轮排列, 且有逆时针和顺时针两种方式。雄蕊的形成是先形成一个环形分生组织, 然后在环形分生组织上以2􊄯5 螺旋产生5 束雄蕊原基, 每一束雄蕊原基的第一雄蕊原基都是在对萼的位置产生, 其它的雄蕊原基在其两侧产生。3 心皮顺序发生, 愈合成3 室单子房, 柱头平截不裂。猪血木与山茶亚科的花器官发生明显不同。

关键词: 山茶科, 厚皮香亚科, 猪血木属, 花器官发生