262 Walter Stiles and Ingvar Jorgensen. 
A most interesting advance in our knowledge of antagonism 
has been recently made by Sziics (35). Regarding antagonism as 
due to the mutual hindrance to one another’s entrance of two 
similarly charged ions he investigates the antagonism between 
copper and aluminium. 1 
For reasons with which we need not deal here, Szucs did not 
determine the death points of the plants upon which he experi¬ 
mented, but the time taken for the plants to absorb enough of the 
toxic substances to kill. In order to do this he made use of the 
geotropic reaction of the hypocotyl arid seedling root as indicator 
of the toxic action. The species used was Curcubita Pepo. After 
varying times of immersion in the solution the seedlings were 
removed and placed with their axes in a horizontal position under a 
bell jar in moist air. After 24 hours the number of plants which 
exhibited the geotropic reaction was noted. A longer period of 
immersion resulted in fewer seedlings responding to the reaction: 
the time of immersion required to kill was taken as the time 
required in order that 70% of the seedlings should no longer 
respond to the reaction. 
This method is open to the objection that owing to the 
differences exhibited in individual plants a very large number of 
seedlings is required in order to get a reliable result in each 
experiment. This difficulty Szucs’ own numbers clearly show ; 
nevertheless the method is decidedly ingenious. 
Szucs shows that aluminium chloride produces a marked 
depoisoning effect upon copper sulphate, the maximum depoisoning 
of a 0*025 N CuS0 4 resulting when a ratio of 0*025 N Cu S0 4 to 
0*15 N A1C1 3 is used. With this concentration of copper sulphate 
when there is less aluminium chloride present the copper sulphate 
is more toxic; with more aluminium chloride the poisonous effects 
of the latter become obvious. 
By boiling the roots, Sziics was able to show by testing for 
copper with H 2 S in acid solution that the antagonism does mean 
that the copper is actually not absorbed. 
In a very interesting series of experiments Sziics investigated 
the depoisoning action of various metals on alkaloid bases. He 
experimented on a species of Spirogyra. Here also was measured 
the time taken for the plant to absorb enough to kill, rather than 
r The depoisoning of copper chloride and copper sulphate by salts of 
ammonium, potassium and sodium in regard to the germination of fungus 
spores had already been shown by Clark (6). For the depoisoning of heavy 
metals by lighter ones see also True and Gies (38) and Le Renard (13). 
Brenchley (4) has also shown that copper sulphate is much less toxic for 
Barley in the presence of nutrient salts than when alone in solution. 
