168 



DROSERA ROTUNDIFOLIA. 



CHAP. VIL 



salts of ammonia which were tried, all cause the in- 

 flection of the tentacles, and often of the blade of 

 the leaf. As far as can be ascertained from the 

 superficial trials with the last six salts, the citrate is 

 the least powerful, and the phosphate certainly by far 

 the most. The tartrate and chloride are remarkable 

 from the short duration of their action. The rela- 

 tive efficiency of the carbonate, nitrate, and phos- 

 phate, is shown in the following table by the smallest 

 amount which suffices to cause the inflection of the 

 tentacles. 



From the experiments tried in these three dif- 

 ferent ways, we see that the carbonate, which con- 

 tains 23'7 per cent, of nitrogen, is less efficient than 

 the nitrate, which contains 35 per cent. The phos- 

 phate contains less nitrogen than either of these 

 salts, namely, only 21 - 2 per cent., and yet is far more 



