42 



VASCULAR CRYPTOGAMS 



the cells of which these trabecules are composed are round, they form a 

 loose spongy parenchyme surrounding the bundle, and sharply differ- 

 entiated from the firm compact fundamental tissue. The stem has 

 one or more cauline ' vascular ' bundles, which may be traced in the 



Fig. ^i.-Sela^inella {ncequalt/olia Spr. A, branch (natural size); B, microsporange ; C, megasporange 



(greatly magnified). 



procambial condition to the apex of the stem close beneath the apical 

 cell and above the youngest leaves : the separate bundles which descend 

 from the leaves (leaf-trace-bundles) only unite with the cauline ones at a 

 later period. The bundles are usually ribbon-shaped, and are concen- 



