LEAF IN THE VASCULAR CRYPTOGAMS AND GYMNOSPERMS. 
615 
Fig. 52. 
Fig. 53. 
Fig. 54. 
Fig. 55. 
Welwitschia mirab ills. 
Longitudinal section of the apex of a seedling about six weeks old, showing 
one plumular leaf in surface view : the depth of the shading in this and 
the next figure is intended to represent the relative intensity of growth, 
and cell-division. X 20. 
Longitudinal section of a seedling about G weeks old, in a direction perpen¬ 
dicular to the planes of the plumular leaves. X 20. 
Transverse sections of successively older plumular leaves. X20. i, ii, iii, 
indicate the bundles of successively formed pairs. 
Ephedra distachya. 
i-iv. Successive transverse sections, from apex to base, of a mature leaf. 
X 20. 
