A TEXT-BOOK OF BOTAXY. 



tilting what is known as the AXXULUS ( Fig. 53, n) . The form of 

 the annulus determines the manner of dehiscence of the sporangia, 

 which occurs on drying. The spores are ejected with consider- 



Fic. 53. Male fern [Dryopteris (Aspidium or Xephrodium) Filix-mas]. A, portion 

 of leaflet showing a number of more or less reniform sori near the mid-vein; B, transverse 

 section through a ripe sori showing clusters of stalked sporangia, which are covered by 

 the indusium (i), an outgrowth of the leaflet; C, a closed but ripe sporangium showing the 

 annulus or ring (n), and the irregular-shaped spores within; D, showing the manner of 

 opening of the mature sporangium and the dispersal of the spores; E, two spores much 

 magnified. After Dodel-Port. 



able force (Fig. 53, D}. They (Fig. 53, E; Fig. 57) are either 

 bilateral or tetrahedral and require a short period to elapse before 

 they germinate. They retain their vitality for a lon^ time, except 

 those which are green, i.e., contain chlorophyll. The spores are 



