188 DROSERA ROTUNDIFOLIA. Cuar. VII. 
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 pre- 
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 
* Miller’s ‘ Elements of Chemistry,’ 3rd edit. pp. 337, 448, 
