85 



The Influence of Certain Environic Factors on the Devel- 

 opment OF Fern Froth allia. 



David M. Mottiek. 



I Abstract.! 



SiMircs of the folliiwiiiij; ferns were used in the exiieiimeuts : Onocleu 

 struthiopteris (L.) Iloffm. Dryopteris stipuhiris (Willd) Maxon and 

 ■"Xeiihriidiuni niolle." 



Irothalliu of (). struthiopteris which liad developed numerous anthe- 

 ridia, l)ut wliicli were nuicli too small to bear archesonia. were trans- 

 l»lant"d to separate dishes and allowed to iirow under favorable condi- 

 tions. Some of these developed into large prothallia and bore archegonia. 

 The fact that female prothallia of this fern, if kept growing for some time 

 without the fertilization of any of the egg-cells, may develop antheridia, 

 has already been recorded in an earlier publication (Mottier. Bot. Gaz., 

 ."!(»: 20; 1-21 ;j, 191(11. 



Sjiores of all of the above named species were found to germinate 

 poorly, or not at all, if the cultures were kept in direct smdiglit in the 

 greenhouse from the time of sowing. In cultures in which prothallia devel- 

 oped, nearly ail plants were small ;uid bore only antherladia, a very few 

 only beconung large enough to produce archegonia. 



Three cultures, A. B. and C, of Onocles struthiopteris vvere sown April 

 :», 1!)11. They were placed in a position to receive direct sunlight, but 

 during the brighter hours of the day clieese cloth was placed over the bell 

 jars under whi<-h the cultures were kept, to diminish somewhat the inten- 

 sity of illumination. On April 30 all three cultures seemed to have made a 

 favorable beginning, the majority of the prothallia being lieart-shaped but 

 not large enough to bear arcliegonia. A and B were now placed in a 

 position in the greenhouse to receive good diffused light, but no direct 

 sunlight save for only a short time in the early morning. Culture C was 

 left in the original position of direct sunlight except the protection given 

 Ity the cheese cloth from about :.30 a. m. to 3:0(1 ]i. m. during days of 

 liright sun. A and B developed into tine cultures, while in C nearly ah 

 plants remained small, bearing antheridia only. 



All cultures were grown hi earthern saucers upon earth which had 

 been previously sterilized in a steam sterilizer. They were watered by 

 means of sul)-irrigation. 



