Fig.
7.2-3. Longitudinal section of vascular bundle in
a club moss (Lycopodium). The vessel elements with annular secondary
walls in corn (Figs. 7.2-1 and 2) are larger than those in most species. This
club moss also produces annularly thickened xylem cells – in this case
tracheids – that are narrow: this is a very high
magnification micrograph. Despite the magnification, the cells are so narrow
that almost no detail is discernable. This size is a somewhat more common than
that in corn.