Observations on the Spore Morphology of Four Species of Selaginellaceae from China

The spores of four species, Selaginella ciliaris (Retz.) Spring, S. kansuensis Ching, S. mutensis Ching and S. trichoclada Alston from China were observed under LM and SEM. The spores are tetrahedral-globose, trilete. The morphological characters of them are described in detail. The spore morphology of the four species is different from each other, especially in spore ornamentation. Of the S. ciliaris (Retz.) Spring, the megaspores have many narrow ridges on the proximal face, freely anastomosing, especcially on the distal face; the microspores are finely rugulate, with many even bacula. Of the S. kansuensis Ching, the surface of the megaspores is rather psilate; the microspores have radiative ridges on the proximal face, lacking micro-ornamentation, and have wide, coarsely verrucate-rugulate ornamentation on the distal face. Of the S. mutensis Ching, the megaspores have many dense granules or tubercles on the proximal face, irregular verrucae coalesce to form coarsely cristae on the distal face; the microspores have tubercles on the proximal face, more, bigger and denser tubercles with foveolae on the distal face. Of the S. trichoclada Alston, the megaspores have tubercles on the surface, sometimes anastomosing on the distal face; the microspores have short, sharp spinules on the proximal face and wide, flat spinules anastomosing on the distal face, with obtuse apex. The surface ornamentation of spore seems to be stable within species and thus is of important value in the taxonomy of the genus Selaginella. The ornamentation of the spore is not easily characterized; however, some types can be recognized. There is generally denser and finer ornamentation on the proximal face than that on the distal face.