Fl(i. ;5. ElTiH^ts i)f tuniiii;;- imilci a. (Tdii dI' \ fUli vlc;;uiniu(>us i iiiion the j;io\\lh of 

 oats. Hoth pots were supijlied with jxitasli ami pliosphorio acid o(|iiall.v, as in 

 Fig. 2. Tlie pot marked " Salpeter" received its nitrogen in tlie form ol' salt- 

 peter ; the one marked "Wickeii" had vetcli tuini'd under, slicuvin'; that it was 

 equal to saltpeter as a source of nitrogen. 



