188 DROSEEA EOTUNDIFOLIA. Chap. YIII. 



and potassium,* which act so differently ; therefore 

 we might expect that its action would be inter- 

 mediate. We see, also, that caesium causes inflection, 

 and rubidium does not; and these two metals are 

 allied to sodium and potassium. Most of the earthy 

 salts are inoperative. Two salts of calcium, four of 

 magnesium, two of barium, and two of strontium, did 

 not cause any inflection, and thus follow the rule of 

 the preponderant power of the base. Of three salts 

 of aluminium, ,one did not act, a second showed a 

 trace of action, and the third acted slowly and doubt- 

 fully, so that their effects are nearly alike. 



Of the salts and acids of ordinary metals, seventeen 

 were tried, and only four, namely those of zinc, lead, 

 manganese, and cobalt, failed to cause inflection. The 

 salts of cadmium, tin, antimony, and iron, act slowly ; 

 and the three latter seem more or less poisonous. The 

 salts of silver, mercury, gold, copper, nickel, and 

 platinum, chromic and arsenious acids, cause great 

 inflection with extreme quickness, and are deadly 

 poisons. It is surprising, judging from animals, that 

 lead and barium should not be poisonous. Most of the 

 poisonous salts make the glands black, but chloride of 

 platinum made them very pale. I shall have occasion, 

 in the next chapter, to add a few remarks on the dif- 

 ferent effects of phosphate of ammonia on leaves j)re- 

 viously immersed in various solutions. 



Acids. 



I will first give, as in the case of the salts, a list 

 of the twenty -four acids which were tried, divided into 

 two series, according as they cause or do not cause 



* ]\Iiller's ' Elements of Chcmiatry,' Srd edit. pp. 337, 4i8. 



