102 OUTLINES OF EVOLUTIONARY BIOLOGY 



FIG. 48. The Sporophyte Generation of a Fern, Aspidium filix mas. (From 



Strasburger.) 



A, section through a sorus or group of sporangia, covered by the indusium (x 20, after 

 Kiiy); B, lower surface of a pinna, showing the indusia covering the sori; C, lower 



Any 



surfi 



ace of a pinna with the sori exposed. 



