PTERIDOPHYTES 



307 



FIG. 176. A fern (Aspidium Filix-mas) bearing sporangia and spores 



A, rhizome and leaves ; fr, young leaves ; B, pinnule with sori (s) ; C, vertical section 

 of a portion of a pinnule (p), showing indusinm (i) and sporangia (s) ; D, single 

 sporangium. After Wossidlo. From Bergen and Davis's " Principles' of Botany" 



inclement conditions. Bower estimates that a large fern plant 

 like Aspidium (Fig. 176) may produce as many as ffty million 

 spores in a season, which are scattered by the above device to 

 perpetuate the particular fern by which they are produced. 



