1 8 Brown: Apogamy in Phegopteris polypodioides 



time stimulated the development of apogamous embryos in 

 this species. 



Woronin ('07) believes dryness to have been the cause of 

 apogamy in the cultures of Pellaea and Nolholaena with which 

 she worked. By growing the prothallia of Pellaea flavens in 

 poor light or on poor soil she was able to secure modifications 

 in apogamous outgrowths, which showed transitions between 

 gametophytes and sporophytes as varied as those described by 

 Lang. 



Yamanouchi ('08), in his study of Nephrodium molle, found 

 that when conditions for fertilization were supplied this species 

 reproduced normally, but that if the cultures were placed in 

 strong light and watered from below fertilization was prevented 

 and apogamous outgrowths were formed instead. 



Outgrowths of an apogamous nature were described by Miss 

 Pace ('10) as occurring on some unidentified prothallia which 

 she kept well watered in bright light. 



Heilbronn ('10), finding that dryness was not the cause of 

 apogamy in the forms he studied, suggested that summer rather 

 than winter cultures were more likely to become apogamous. 

 But his investigations with different qualities and intensities of 

 light, in moist cultures and at a high temperature, did not 

 verify these conclusions. 



Schlumberger ('11) found that by decreasing the moisture 

 for old prothallia of Woodsia ilvensis, whose vitality had become 

 lowered by the growth of algae and fungi in the cultures, the 

 production of apogamous outgrowths was induced. He believes 

 the observed enlargement of the apices of these apogamous 

 outgrowths to be analogous to that described for Anogramma 

 chaerophylla by Goebel ('97), who considered their development 

 to be an adjustment on the part of the plant to the unfavorable 

 environmental conditions caused by dryness. 



Allen ('11) found apogamous sporophytes occurring on pro- 

 thallia of Aspidium falcatum which had been grown in pots of 

 red clay surrounded by sphagnum or moist sand, and kept either 

 in a Wardian case or under bell jars for five, six, and in one case 

 eleven months. These prothallia were not watered from above, 

 the water in the sphagnum or sand keeping the clay uniformly 

 moist. 



