124 



Elementary Biology. 



a single linear series. The capsule consists of a single layer 

 of thin squames enclosing a space, filled in the mature sporan- 

 gium by a large number of spores. The cells of the wall of 



FIG. v.AspidiicmJilix-nias. .(Sachs.) 



A, section of leaf with sorus ; s, sporangia ; /. indusium. B, young sporangium ; 

 r, annulus. c, mature sporangium containing spores ; d, glandular hair. 



the sporangium are modified in one region, so as to form what 

 is known as the annulus. The row of cells composing it have 

 their walls greatly thickened and are of a dark brown colour. 

 Rupture of the thin parietal cells is brought about by drying 



