The Determinative Action of Environic Factors Upon Neobeckia acquatica 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 frorn those of ordinary water. Recourse was then taken to 
water cultures with unusual proportions of potassium nitrate. Nany of 
these were made and as the results were fairly uniform the 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 
100 grams 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 ensues 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 
