52 INFLUENCE OF CHEMICALS 



contractile, or motile functions of the protoplast, but not all of the 

 other functions, especially those essentially metabolic in their na- 

 ture. Thus it has been found by recent investigations that plants 

 show an increase in respiratory activity under the influence of 

 anaesthetics. 1 The probability may be admitted that not all sub- 

 stances which have a narcotic or anaesthetic action upon living 

 matter, are catalytic in their action ; direct chemical combination 

 may be made with some of the substances in the cell. 



77. Poisons which Form Salts. Some substances are poison- 

 ous to protoplasm by forming salts with its constituents. Among 

 these are acids, mineral bases, and salts of heavy metals. The 

 organic acids are not so powerful in their action in general as the 

 inorganic, but both are very deadly in the minutest quantity to 

 certain forms of plants, especially algae. 



The poisonous effect of the mineral bases may sometimes be due 

 to the purely physical action, such as osmotic attraction by which 

 water or organization may be withdrawn from the colloidal mass 

 of living substances so extensively as to cause its disorganization. 



By the recent researches of True and Kahlenberg it has been 

 found that the toxic action of dissolved salts and acids depends 

 to a great extent upon their dissociation when put into solution in 

 water. The undissociated molecules will exert their own proper 

 effect upon the protoplasm, with the added effect of the separate 

 ions of the dissociated portion of the substance. Furthermore, 

 the ions may combine to form complex ions with a still different 

 and separate effect. Mercuric cyanide is an example of a sub- 

 stance which is not dissociated in solution. Its poisonous effect 

 is therefore due solely to the proper chemical effect of its entire 

 molecules. Lupines were found to survive with their roots im- 

 mersed in a solution of ^o^To gram molecule per liter. Silver 

 nitrate, on the other hand, is strongly dissociated in solution, acting 

 through its ions. The roots of the lupine will endure only ^rg^-jry 

 gram molecule per liter of this substance. 



1 Morkowine, N. Recherches sur l'influence des anesth&iques sur la respiration 

 des plantes. Rev. Gen. Bot. II : 289, 341. 1899. 



