THE VASCULAR CRYPTOGAMS 



39 



towards the top, till a constant diameter is attained 

 (Fig. 17). This is commonly the case in plants which 



a 



FIG. 17. General view of the Male Fern, a, apex, b, base of stem, 

 which is covered with the remains of old leaves, and bears 

 numerous adventitious roots ; c, c, young leaves, showing 

 circinate vernation. Greatly reduced. 



have no secondary growth in thickness, and in which, 

 therefore, the increase in bulk must depend entirely on 



