Cuav. VIIL] CONCLUDING REMARKS, SALTS. 153 
quite inefficient. The great power of the former is probably 
due to the presence of phosphorus, as in the cases of phos- 
phate of lime and of ammonia. Hence we may infer that 
Drosera cannot obtain phosphorus from the phosphate of 
potash. This is remarkable, as I hear from Dr. Burdon 
Sanderson that phosphate of potash is certainly decomposed 
within the bodies of animals. Most of the salts of soda act 
veryrapidly ; the iodide acting slowest. The oxalate, nitrate, 
and citrate seem to have a special tendency to cause the 
blade of the leaf to be inflected. The glands of the disc, 
after absorbing the citrate, transmit hardly any motor impulse 
to the outer tentacles; and in this character the citrate of 
soda resembles the citrate of ammonia, or a decoction of 
grass-leaves; these three fluids all acting chiefly on the 
blade. 
It seems opposed to the rule of the preponderant influence 
of the base that the nitrate of lithium causes moderately 
rapid inflection, whereas the acetate causes none; but this 
metal is closely allied to sodium and potassium,* which act 
so differently; therefore we might expect that its action 
would be intermediate. 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 
doubtfully, 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 cad- 
mium, 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 quick- 
ness, 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 
* Miller’s ‘Elements of Chemistry,’ 3rd edit. pp. 337, 448. 
