Abstract: Limnocharis flava ( Linn. ) Buch. normally produced 2 ～ 13 bisexual flowers in a cincinnus (seorpioid cyme). The anthesis of each flower lasted 5 ～ 13 hours. In natural populations, two species of beetles were observed visiting the flowers in bloom. Several whorls of staminodes outside of the stamens limited the pollen to disperse outward, and made the pollen deposit only on the stigma of the same flower. After the perianth closed, the inner perianth changed into liquid which created a suitable environment for pollen germination. The pollen-ovule ratio, which ranged from 650 to 1120( 930±180) reflects an economical self-pollination system. As the fruits maturied, the inflorescence fell to ground or mud, and the vegetative buds (i.e. vegetative components ), developed at the apex of the inflorescence, grew into new vegetative shoots. One mother plant usually could produce 6 ～ 20 new vegetative shoots in a life cycle. One fruit of L. flava contained 470 ～ 640 seeds, with an average seed-set rate of about 80%. The seeds of Limnocharis flava could disperse a long distance and occupy new suitable habitats to establish new populations. The vegetative buds, however, predominantly could only spread to nearby places and thus enlarge the size of the population. Results from some artificial treatments, such as emasculating and netting, emasculating and bagging, hand-pollinating, netting, and bagging, indicate that L. flava is selfing in general but also cross-compatible. Based on the above results, it is considered that the breeding system of L. flava is predominantly selfing, but mixed with outcrossing, and the likely evolutionary tendencyis from outcrossing to selfing.

Key words: Limnocharis flava (Linn.) Buch., Breeding system, Self-pollination, Evolution