THE VASCULAR CRYPTOGAMS 



39 



towards the top, till a constant diameter is attained 

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



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 



