Abstract: The capsules of Calanthe tsoongiana T. Tang et F. T. Wang. in different development stages were collected and the growth dynamic of the fruits was studied. The anatomical development was observed by the method of paraffin sections. The results showed that the first 40 days is the fastest growth period of capsules. C.tsoongiana is tricarpellate, showing a pattern of six valves in cross section: three fertile and three sterile. The six half-carpels remain joined at the apex. The increase in the fruit diameter results mainly from cell division between valves and the increased volume of mesocarp cells and not from the number of cell layers. The volume of exocarp and endocarp remain unchanged in different development stages. In the mature fruit of C.tsoongiana, only a few cells show parietal thickening. The precursor cells of the dehiscence line become lignified on their cell walls in mature fruits, the fertile and sterile valves contract in opposite directions, resulting in a longitudinal rupture.

Key words: Calanthe tsoongiana, carpel, placenta, pericarp