(61

(61

Ch XI.

a plant by a single shower of rain; & yet all physiologists admit that such ammonia is absorbed by its the roots. Nor is it surprising that Drosera should eagerly desire & profit be enabled to be nourished be enabled to profit by the salts of ammonia, for yeast &otherlow fungoid forms flourish if in a such solutions; if the othernecessary elements are given by them present. But it is an astonishing fact, on which I will not here again enlarge, that so inconceivably minute a quantity as the one .30-milllionth of a grain of anhydrous phosphate of ammonia should induce some change, in a gland of Drosera, sufficient to cause a motor impulse to be sent down almost the whole length of the tentacle tentacle pedicel; this impulse b exciting its movement the pedicel to be move often through an angle of above 180 degrees. I know not whether to be most astonished at this fact, or that the pressure on a gland of one end of a minute bit of hair, weighing only the 1/78,700 of a grain, & largely supported by the dense secretion, should quickly cause a

(62

(62

Ch XI.

as few plants are at present known to possess glands specially adapted for absorption, it seemed worth while to try the effects on Drosera of various salts & acids. The dose ordinarily administered to the gl was the 1/960' of a grain in a so drop placed on the disc. The results are given in the eighth chapter. We there see that the physiological power of those salts which were tried does not accord with the their ordinary chemical classification. commonly adopted. The nature of the basis is far more important influential than that of the acid; & this is known to hold good with animals. There For instance nine salts of sodium all caused inflection & none of those in small doses were poisonous; whereas seven of the corresponding salts of potassium had no such effect did not cause inflection, & two only to a slight degree; some of them in similar doses were moreover poisonous. It is known that There is a like great difference between the effects of the salts of sodium & potassium, when injected into the circulation blood of animals. The so-called earthy salts are inoperative produce hardly any effect on Drosera. On the other hand most of the metallic salts induce cause rapid & strong strong inflection, & are deadly poisonous; but there are some odd