ASSIMILATION OF CARBON 39 



appearance of starch but prevent its continued accumulation; others (0.5 per 

 cent, of caflein) favor the accumulation of starch. 



Experiments in which green plants were supplied with organic nitrogenous 

 compounds, in a chamber free from carbon dioxide, gave negative results.* 



1 Grafe, Victor, Ufitersuchungen uber die Aufnahme von Stickstoffhaltigen organischen Substanzen 

 durch die Wurzel von Phanerogamen bei Ausschluss der Kohlensaure. Sitzungsber. (math.-naturw. Kl.) 

 K. Akad. Wiss. Wien xi&^ : 1135-1153. 1909, 



