I06 PROCEEDINGS OF THE COTTESWOLD CLUB 



From this date the experiments were unavoidably inter- 

 rupted for so long a period as ten years by the removal of 

 Dr Hellriegel from Dahme, and by other pressing occupa- 

 tions. In 1883, however, at a new experimental station at 

 Bernberg the collaboration was resumed and our experi- 

 menters returned to their old task. 



It should here be noticed that the attention of other 

 observers had about this time been called to the same 

 subject, and much was being done to its elucidation in 

 various parts of the world, but we may with advantage to 

 the narrative, follow to its conclusion and completion the 

 work of Hellriegel and Wilfarth, and return later to the 

 contemporary results of other original workers in the same 

 field. 



The years 1883-5 were employed in picking up the 

 threads of the old work, and repeating again with such 

 additions and precautions as experience suggested the old 

 experiments on barley, oats, and peas. 



Some brief account of the methods employed will aid 

 us in appreciating the subsequent course of the important 

 investigations. The difficulties of conducting with absolute 

 thoroughness an extended series of observations of this 

 nature are manifold and serious, the factors to be esti- 

 mated and valued are so numerous. 



The medium in which the plants were grown was a 

 fine quartzose sand from Tertiary Beds at Oberlausitz, 

 in Saxony. The sand was not quite chemically pure, 

 containing traces of lime, magnesia, potash, soda, and 

 phosphoric acid. But the amount of Nitrogen present 

 was always most carefully determined, and was found to be 

 almost infinitesimal, and "negligeable" in the estimation of 

 results. 



Glass jars of two sizes made of white glass wath larger 

 or smaller holes in the bottom were employed for growing 

 the plants in. We may use the term "pots' for them. In 

 the bottom of each pot were placed for drainage purposes 



I 



