CHAP. IX. EFFECTS OF PREVIOUS IMMERSION. 



215 



In a large majority of these twenty cases, a varying degree of 

 inflection was slowly caused by the phosphate. In four case8, 

 however, the inflection was rapid, occurring in less than half an 

 hour or at most in 50 m. In three cases the phosphate did not 

 produce the least effect. Now what are we to infer from these 

 facts? We know from ten trials that immersion in distilled 

 water for 24 hrs. prevents the subsequent action of the phos- 

 phate solution. It would, therefore, appear as if the solutions of 

 chloride of manganese, tannic and tartaric acids, which are not 

 poisonous, acted exactly like water, for the phosphate produced 

 no effect on the leaves which had been previously immersed 

 in these three solutions. The majority of the other solutions 

 behaved to a certain extent like water, for the phosphate pro- 

 duced, after a considerable interval of time, only a slight effect. 

 On the other hand, the leaves which had been immersed in the 

 solutions of the chloride of rubidium and magnesium, of acetate 

 of strontium, nitrate of barium, and citric acid, were quickly 

 acted on by the phosphate. Now was water absorbed from these 

 five weak solutions, and yet, owing to the presence of the salts, 

 did not prevent the subsequent action of the phosphate? Ox 

 13 



