Wolffia is the aquatic, the simplest and the smallest angiosperm in the world. The body of Wolffia consists of only one leaf and a few buds wrapped by the leaf (picture 1-2). Under normal conditions, Wolffia is doing vegetative growth without sexual reproduction. In our lab environment, many chemical reagents could induce W. australiana flowering (EDTA, GA3, SA, 6-BA). The 6-BA is the best one (picture3) . One mall hole was shown in the "deck" of the boat-like leaf (picture 4), it was the first sign of flowering, then one stamen and one gynoecium reached out (picture 5-6). Also, there was a bubble covering the stigma at an early stage, and it would exploded later (picture 7-8). Gynoecium had grown as big as whole plantlet at late stage (picture 9-10), however, we have not got seed yet.

SEM pictures showed overall appearance (picture1) of W. Australiana and primordium (picture 2), stomata (picture 3) and the petiole in the hole (after plantlet abscised) (picture 4). Some details of flowered W. Australiana were shown in picture 5-7.

In the TEM pictures of the W. Australiana, several branches could be observed. The plantlets stood in a line from big to small, which suggested that the branched plantlets are initiated sequentially(fig.1-5). Partial enlarged view of the small branches are shown in fig.4,5,7, and continuous cell cluster of the smallest ones may be the place primordium initiated. In some big primordium, a crack can be observed (Fig. 6), where will be new primordium of the branched plantlet initiated. Primordium of the pistil and stamen could be also found next to the branch(fig.7,8), which indicated that they all originate from the same cells.