Stem
The stem of a seedling has two major features. One feature is long "hair" of the stem (red in the upleft figure and purple in the down right figure). The other one is small and "bread" shape(yellow green in both figure). For lack of a better word, I would call the long one spike, and the small one baby spike.
The leftdown figure shows a small spike on the stem. This picture is taken at the tip of the seedling, where the skin morphology accords with previous graphs. I believe that the spike grows from babyspike (that is why I call it babyspike). The middle-down figure shows the tip of a grown spike.
Bi-focus image assembling
The left and middle graph are focus on different spike. The right figure is assembling from them.
The graph at Bean -> Bean and Skin -> Figure 4 is also done in this way. In that case, 4 graphs are assembled so it is more challenging. Due to the depth in that graph, it is really difficult to focus well. Anyway, the final image is more pleasant than original ones, although not excellent.