METALLIC POISONS 87 



that treatment with dilute chloroform followed by washing in water will 

 usually cause streaming to appear in cells which have a tendency to this 

 form of activity. Both chloroform and ether probably enter into loose 

 union with certain of the constituents of the protoplasm, and their action 

 upon streaming is simply the result of their general action upon 

 metabolism. 



SECTION 38. Metallic Poisons. 



As in the case of acids and of such substances as sodium and calcium 

 chlorides in which the acid ions seem to play the poisonous part, all con- 

 centrations sufficient to produce any effect cause from the outset progressive 

 retardation, which may be preceded by a temporary shock-stoppage if the 

 poisonous solution is moderately concentrated and suddenly applied. 



Dilute solutions of sodium chloride are comparatively innocuous to 

 most plants, and indeed the presence of this salt forms one of the con- 

 ditions for the development of most marine algae. Plants of Chara 

 and Nitella, however, which had been kept for some time in nearly pure 

 water, ceased to show streaming, and ultimately died in solutions con- 

 taining from 01 to 0-5 per cent, of salt. That this is a toxic effect is 

 shown by the fact that partial plasmolysis occurred only in 2 per cent, 

 solutions. With regard to copper sulphate, which, according to Nageli 1 

 acts as a powerful poison in excessive dilution, apparently contradictory 

 results to those of Nageli have been obtained by Klemm and by the 

 author. Klemm (1. c., p. 43) found that hairs of Momordica still exhibited 

 weak streaming after an hour in 10 per cent. CuSO 4 . 2 The same is the 

 case with hairs of Cucurbita, with hairs of Trianea in 2 per cent, 

 and with Chara and Nitella in 0-5 per cent, solutions. In all cases the 

 CuSO 4 appears to penetrate the protoplast, and in Momordica and 

 Trianea it accumulates in the cell-sap by a process of passive secretion. 



The explanation of the temporary resistant power is that (i) the 

 full poisonous action is only slowly exercised ; (2) the relative percentages 

 of free ions to dissolved salt are less in concentrated than in dilute 

 solutions ; (3) the salt acts as a cumulative poison, so that a subminimal 

 external percentage may accumulate slowly internally until the poisonous 

 percentage is reached. This is shown by the fact that large masses of 

 Chara, Nitella, or Spirogyra, are unaffected by immersal in small quantities 

 of O'Oi per cent. Cu SO 4 , whereas in large quantities of the same solution 

 they die in from one to a few days. 



Penicillium is able to grow upon nutrient solutions containing 5 to 



1 Oligodynamische Erscheinungen, 1893 (Denkschr. d. Schweiz. Naturf.-Ges.), Bd. xxxill. 

 3 The presence of a cuticle naturally diminishes the amount of poison penetrating the proto- 

 plasm in unit time. 



