129 



Studies of Camptosorus rhizophyllus, an abstract 



OF The Development of the Prothallium of 



Camptosorus rhizophyllus,* and The 



Resistance of the Prothallia of 



Camptosorus rhizophyllus 



TO Desiccation.! 



F. L. Pickett. 



As is well known the Walking Fern, Camptosorus rhizophyllus, is 

 found chiefly on rocky ledges in more or less shaded places, where the 

 water supply is irregular and slight at all times. The colonies in the 

 neighborhood of Bloomiugton, Ind., have abundant water supply only at 

 times of heavy rain and of course enjoy such supplies for but brief periods. 

 The fact that this fern could not only withstand the many longer or 

 shorter periods of drought but could multiply in the regular way under 

 such conditions suggested the probability of some special sti'uctural or 

 physiological adaptation. The scheme for vegetative increase by means of 

 stoloniferous leaves is well known and gives the plant its specific name. 

 But the presence of many small plants which could not have had such 

 origin and so must have been produced through the production of the 

 prothallia 1 or sexual stage, along with the fact that the prothallia of 

 many of our ferns cannot survive the lack of a normal supply of moisture 

 for more than a few hours, suggested another possible adaptation as well 

 as a point of attacking the problem. 



Cultures were made ot sowing spoi-es on steiilized soil in clay saucers 

 protected under bell jars. Both the peculiarities of form and the resist- 

 ance to desiccation were studied. 



The following peculiarities of tovm and developniont have been noted. 

 The development of a plate of cells is not uniform, beginning sometimes 

 immediately after the germination of the spore and at other times not 



*Bot. Gaz., 57: 228-2.38, Mar., 1914. 



tBuU. Torr. Bot. Club, 40: 641-645, Nov., 1913. 



9—1019 



