200 BOTANICAL GAZETTE [MARCH 
improvement in a o.1 per cent solution of KCI (III, 14), in a 0.02 
per cent solution of MgSO, (III, 15), and in a mixture with an 
equal volume of tap water or an equal volume of ordinary distilled 
water (IIT, 16), over such solutions without the colloidal platinum. 
It also, as has been shown above, produced improvement in a weak 
colloidal solution of silver and in a solution of NaOH. The addi- 
tion, however, of 0.008 per cent PtCl, to a 0.02 per cent solution of 
MgSO, produced no improvement in this solution (III, 17). 
A few experiments were made with other algae. Spirogyra 
decimina Kg.,3 newly brought to the laboratory, gave practically 
the same results as those already described, except that it was more 
quickly injured by colloidal gold solution (IV, 18-23). However, 
filaments of a species of Oscillatoria growing in o. 5 per cent Sachs’s 
solution thickened with 1 per cent agar, when transferred to the 
gold solution remained in pet- 
fect condition and continued 
their usual movements during 
. Spirogyra longata from the period of the experiment 
eal creat shoei after rane = ( 3-4 days) (IV, 24). : 
mike When filaments of Spirogyré 
longata from the stock culture 
or filaments of S. decimina were placed in colloidal gold solution, @ 
striking phenomenon was observed; the outer layer of the cell walls 
swelled irregularly within 17 hours, forming gelatinous sheaths over 
considerable portions of the external surfaces (fig. 1). These 
sheaths, whether greatly swollen or not, were colored purple by the 
' gold solution. The cells remained in otherwise excellent condition 
during this time; their contents were uncontracted and normal in 
appearance, and the chloroplasts retained their usual green color. 
That the cells were alive and healthy was indicated by the fact 
that they were easily plasmolyzed by glycerine. When filaments 
of S. longata were examined directly in the gold solution, they 
showed slight irregular swellings (fig. 1), but when transferred from 
the gold solution to glycerine solution or to non-toxic distilled watet 
marked swelling became evident over the entire wall within one OF 
Siiss- 
3 Determined from O. KrrcHNer, Die mikroskopische Pflanzenwelt des 
wassers. 1885. 
