Developing capsules of C. macranthos were collected from the
natural population at Bai Hua mountain (1800 m above sea level),
Beijing, China. Anthesis usually occurs in June, each year. For good
capsule setting (approximately 80–95%), the flowers were labeled
and hand-pollinated by transferring the pollinia onto the stigma of
the same flower as the flowers fully opened (Fig. 1). After capsule
setting, at least five capsules were collected at a two-week interval (six different developing stages) for the histological study and
asymbiotic seed germination experiments