THE PTERIDOPHYTA : FILICALES, THE FERNS 



495 



it has subsequently been elucidated in nearly every group, so that the name 

 Cryptogam is now an obsolete survival. 



The mystery surrounding the reproduction of Ferns was realized even 



Fig. 484. — Dryopteris filix-tnas. Mature 

 rhizoids, among which are antheridia 

 cushion behind the growing point. 

 Alternation of Generations in Ferns.) 



prothallus seen from below showing 

 and, above, archegonia arising on the 

 (After Suminski, who first discovered 



in early times, and " fern-seed " figures along with other equally unobtainable 

 commodities in many magical formulae of the Middle Ages. 



Development of the Sex Organs 



The male sex organs, or antheridia, appear while the prothallus is still 

 quite small, and in poorly developed specimens they may be the only ones 

 formed, that is to say, the prothallus is unisexual. But in well-grown 

 prothalli the female organs, or archegonia, develop later on the under side 

 of the central cushion. Both are multicellular structures in which the gametes 

 are enclosed and protected until they are mature. The archegonia are 

 developed behind the notch in which lies the apex of the prothallus, while 

 the antheridia are found farther back among the rhizoids, i.e., near the 

 posterior end of the prothallus. As the antheridia mature before the 



