Abstract: Educing and observing the stem's secondary xylem of Sorbus pohuashanensis revealed two types of perforation plates, simple porforation plate and reticulate perforation plate. There are 5 transition types. There are 3 types of vassel elements:both ends are reticulate type;one end is reticulate type, the other simple type;both ends are simple type. The transform of perforation plate types in ontogenesis process of Sorbus pohuashanensis recapitulates the evolution process of perforation plate from reticulate type to simple type in phylogeny.

Key words: Sorbus pohuashanensis, reticulate perforation plate, simple perforation plate