The Determinative Action of Environic Factors Upon Neobeckia anquattca Greene. 275 



a series of special tests were made to determine under what experi- 

 mental conditions rejuvenescence, as indicated by the formation of 

 nepionic leaves might be induced. Cultures in tap water to ^calcium 

 nitrate had been added in various proportions failed to show any results 

 different from those of ordinary water. Recourse was then taken to 

 water cultures with unusual proportions of potassium nitrate. Hany of 

 these were made and as the results were fairly uniform^ tlie behavior 

 of the plants may be best illustrated by citation of certain selected 

 examples. 



A glass aquarium in the greenhouse at the New York Botanical 

 Garden was filled with 20 liters of water and to this was added 



r 



100 grains of potassium nitrate, on May 23, 1903. Small plants grown 



Fig. 13. Cutting of Neobeckia which was 

 producing finely divided aquatic leaves which 

 after being placed in solution of potassium 

 nitrate formed a series of leaves with 



broader laminae. 



Fig. 14. Terrestrial stem of Neobeckia 

 showing series of leaves in which a 

 simplification first ensuoB then pro- 

 gression toward division of the la- 



minae. 



as aquatics but rooted in small pots of soil were set in the solution 

 so as to be completely submerged. These plants were producing the 

 finely divided leaves of the filamentous type at time of the change. 

 The first leaves produced in submergence in every instance were less 

 refined than those formed last, then others followed with coarser divisions 

 until the ovate-serrate type recognizable as true nepionic forms were 

 developed. These were the beginning of a series which finally returned 

 to the finely divided filamentous type (Fig. 13; see also Fig. 14). 



A more concentrated solution was next made by adding 2 kg of 

 potassium nitrate to 20 liters of water in a glass aquarium. The osmotic 



