710 



U. Ndf 



plenioids, Pteroids (5), Onocleoids, Blechnoids, Dryopteroids (9), 

 Gymnogrammoids (6), and the Woodsioids (11). Among nonpoly- 

 podiaceous species, only Dennstaedtia pinictilobula (Dicksoniaceae) 

 was found to be responsive. The substance failed to promote anther- 

 idium formation even at the highest available concentration (i^ 

 strength Pteridium medium that was active toward the prothalli of 

 Onodea sensihiUs to a dilution of 1:30,000) in the following fern 

 species: Polypodium aureum (Polypodiaceae), Lygodiinn japonicum, 

 Anemia phylUlidis (Schizaeaceae), Osmunda claytoniana, and O. cin- 

 namomea (Osmundaceae). 



Studies on fern species that were unresponsive toward the Pterid- 

 ium factor led to the demonstration of a substance that controls 



■^\ 





A 



B 



"h' 



\ 



t 



v- 



9 



D 



^■^T^:^:- 



Fig. 1. A. Gametophytc ol Oiioclea sejisibilis, 19 days old, 33 X, gr()\\n in tlie 

 presence of Pteridium medium 1:250. B. Same as A, except grown in the absence 

 of Pteridium medium. C. Incipient ameristic prothallus of Pteridium aquilinum, 

 20 days old, 55 X. D. Gamctopliytc of Anemia pliyllitidis, 12 days old, 91 X, grown 

 in the presence of Anemia medium 1:30. E. Same as D, except grown in the ab- 

 sence of Anemia medium. F. Ganictopliyte of Anemia plixllitidis, 25 days old, !! X. 

 G. Ganu'i()|)li\tc of Anemia phylUtidis, 35 days old, 30 X. 



