Chxp. VIII.] CONCLUDING REMARKS, SALTS. 163 



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 

 very rapidly; the iodide acting slowest. The oxalate, ni- 

 trate, 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 im- 

 pulse 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 acetic 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 

 aUied 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 the zinc, lead, mangan- 

 ese, and cobalt, failed to cause inflection. The salts of cad- 

 mivma, tin, antimony, and iron act slowly; and the three 

 latter seem more or less poisonous. The salts of silver, mer- 

 cury, gold, copper, nickel, and platinum, chromic and arseni- 

 ous acids, cause ^reat 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 plati- 

 num made them very pale. I shall have occasion, in the 

 next chapter, to add a few remarks on the different effects of 

 phosphate of ammonia on leaves previously immersed in va- 

 rious solutions. 



1 Miller's ' Elements of Chemistry,' 3rd edit. pp. 337, 448. 



