Fig. 7.4-3. Transverse section of fern rhizome. Most ferns have xylem that consists of tracheids rather than vessels, and in general, tracheids tend to be narrower than vessels. Some plants do have narrow vessels, so to be absolutely certain, it is necessary to see if perforations are present or not, and that is more easily done in longitudinal section rather than a transverse section like this one.