Chap. XL GENERAL SUMMARY. 273 



sponding salts of potassium produced no effect, two 

 causing slight inflection. Small doses, moreover, of 

 some of the latter salts were poisonous. The salts 

 of sodium and potassium, when injected into the veins 

 of animals, likewise differ widelv in their action. The 

 so-called earthy salts produce hardly any effect on 

 Drosera. On the other hand, most of the metallic 

 salts cause rapid and strong inflection, and are highly 

 poisonous ; but there are some odd exceptions to this 

 rule; thus chloride of lead and zinc, as well as two 

 salts of barium, did not cause inflection, and were not 

 poisonous. 



Most of the acids which were tried, though much 

 diluted (one part to 437 of water), and given in small 

 doses, acted powerfully on Drosera ; nineteen, out of the 

 twenty-four, causing the tentacles to be more or less 

 inflected. Most of them, even the organic acids, are 

 poisonous, often highly so ; and this is remarkable, as 

 the juices of so many plants contain acids. Benzoic 

 acid, which is innocuous to animals, seems to be as 

 poisonous to Drosera as hydrocyanic. On the other 

 hand, hydrochloric acid is not poisonous either to 

 animals or to Drosera, and induces only a moderate 

 amount of inflection. Many acids excite the glands to 

 secrete an extraordinary quantity of mucus; and the 

 protoplasm within their cells seems to be often killed, 

 as may be inferred from the surrounding fluid soon 

 becoming pink. It is strange that allied acids act 

 very differently : formic acid induces very slight in- 

 flection, and is not poisonous ; whereas acetic acid of 

 the same strength acts most powerfully and is poi- 

 sonous. Lactic acid is also poisonous, but causes 

 inflection only after a considerable lapse of time. 

 Malic acid acts slightly, whereas citric and tartaric 

 acids produce no effect. 



