SPORES 79 



(singular, sporangium). A sporangium consists of a rounded 

 body composed of a wall, one cell in thickness. A single row 

 of the wall cells is modified to form the annulus. The cells 

 composing the annulus have thick inner and side walls which 

 are very hygroscopic and open the sporangium at the lip 

 cells to permit the escape of the spores. 



FIG. 43. Filicale. Early stages of the young sporophyte which develops 

 as a result of fertilization. 



Spores. In most ferns the spore-bearing tissue is composed 

 of sixteen large cells, which by dividing twice give rise to 

 sixty-four cells. All of the sixty-four cells develop into 



