1914] HOYT—COLLOIDAL METALS 205 
seemed to be unaffected by the colloids; but when swelling occurred 
in the outer portions of the cell walls, as in a mixture of gold 
or platinum with NaOH, the swollen portions became deeply 
colored. In these cases the appearance of the colored wall was 
similar to that produced by the action of a soluble stain like 
Bismarck brown, a feature which suggests specific adsorption of the 
Suspensoid as the cause of this color change. BRepIG (2) and 
ZSIGMONDY (16) mention similar instances of the staining of fungi 
by colloidal gold. In the former case this was not taken into the 
ments but was deposited on the external surfaces of the walls. 
In the latter case the gold continued to be absorbed until the 
solution became entirely decolorized. 
Apparently the only other published work on the effect of 
colloidal metals on plants other than bacteria is that of GALEOTTI 
(6). This author carefully studied the effect of colloidal solutions 
of copper on a species of S pirogyra and compared with these the 
effect of CuSO, solutions computed to contain the same amounts of 
copper in the ionic condition. GaLEotti found colloidal copper 
Poisonous at lower concentrations than was ionic copper, although 
the action of the former was less rapid. The author concluded that 
ionic copper produced a rapid effect by combining with the pro- 
toplasm, while the colloidal metal, at least in lower concentrations, 
Was slowly active as a catalyser, accelerating certain breaking-down 
Processes within the cells. Addition of o.o1 per cent of NaCl to 
higher concentrations of colloidal copper rendered these somewhat 
less toxic and almost entirely corrected the toxicity of the colloid in 
lower concentrations. The toxicity of ionic copper, on the other 
and, was not modified in the presence of o.o1 per cent of NaCl. 
influence of the chloride in diminishing the toxic effect of 
colloidal copper was attributed to some change induced in the 
colloid itself, 
_ Following Gargortr, it may be suggested that the diminution 
i the toxicity of the lower concentrations of colloidal silver, brought 
about in the present studies by the inorganic salts of Crone’s solu- 
tion, may have been due to some action of the salts upon the colloid. 
The effect of animal charcoal and of colloidal platinum upon the 
toxicity of colloidal silver, that of colloidal platinum upon the 
