Spores of 61 species and 6 varieties in 9 genera of the Sinopteridaceae were examined
under scanning electron microscope (SEM). Based on surface ornamentation and other features, the
spores of the Sinopteridaceae are divided into three types. In type Ⅰ , the exospore is smooth and
the surface ornamentation, which is reticulate, cristate, echinate or rugate, is formed by the peris-
pore. All the other genera of this family, except for Onychium and Cryptogramma, have this pat-
tern of spores. In type Ⅱ, the surface ornamentation is formed by both perispore and exospore. This
pattern is found only in Cryptogramma. In type Ⅲ, the perispore is thin and the surface ornamenta-
tion is formed by the exospore. Onychium is characterized by this type of spores. Those genera with
spores of type Ⅰ of the Sinopteridaceae seem to be closely related to each other and should be natu-
ral members of this family. The systematic position of Cryptogramma and Onychium, with spores of
type Ⅱ and type Ⅲ respectively, however, should be reconsidered. Aleuritopteris might be the most
primitive member of the Sinopteridaceae from the evidence of spore morphology.
