Abstract: A field investigation was conducted on the floral syndrome and pollination characteristics of
Iris japonica Thunb. in artificial populations by continuous observation, out-crossing index, pollen-ovule ra-
tio and fruit-setrat. The main results are as follows: Under artificial culture conditions, the population come
into bloom from Febrary to April and the flowering span among populations is 62 days. The flowering span for
a plant is 9 -28 days. The life span of one single flower was approximately 36 -48 hours. The stamen was
close to the lateral side of the petaloid style and 0.32 cm shorter than the style, and the relative position be-
tween the stamen and style was always unchanged in the whole flowering process. The out-crossing index was
4, P /O was about 275.68, combined with the result of the bagging and artificial pollination experiment, the
breeding system of those species was given priority to out-crossing, part self-compatibility, insects pollinator-
dependent. The special floral structure may be the reasons that those species have a low setting percentage.

Key words: Iris japonica Thunb., floral syndrome, out-crossing index, pollen-ovule ratio, breeding  system