204 BOTANICAL GAZETTE [MARCH 
either species of Spirogyra in a o.o1 per cent solution of AuCl, 
which contained also 0.02 per cent or 0.01 per cent. NaOH (V, 3, 
4). When filaments of S. longata were subjected to the action of 
the sodium hydrate of the gold solution (approximately 0.02 per 
cent concentration of NaOH), in the absence of the colloidal gold, 
no swellings were developed (V, 5). Diluting the sodium hydrate 
solution by adding an equal volume of non-toxic water was without 
effect (V, 6a). S. decimina, however, produced some colorless 
sheaths on the second day in this 0.01 per cent solution of NaOH, 
though the majority of the filaments were by this time dead. No 
sheaths were evident on the first day (V, 6b). In sodium hydrate 
solutions with concentrations of 0.02 and o.o1 per cent, respec- 
tively, prepared at another time and perhaps not exactly similar to 
the solution in which the colloidal gold was formed, neither species 
of the alga exhibited any swellings (V, 7, 8). 
With colloidal platinum no sheaths were formed by Spirogyra 
longata in the undiluted solution (V, 9), nor were they evident in this 
solution diluted with an equal volume of tap water (V, 10) or with 
an equal volume of a 0.02 per cent solution of NaOH (V, 11a). In 
this alkaline platinum solution S. decimina, on the contrary, formed 
heavy sheaths within 7 hours, these being colored a deep brown by 
the platinum (V, 11d). Similarly S. Jongata gave only slight sheaths 
on but a few filaments in slightly-diluted platinum ‘solution con- 
taining 0.02 per cent of NaOH; it failed to produce any sheaths at 
all in platinum solution to which 0.01 per cent of NaOH had been 
added (V, 13a). S. decimina formed heavy brown sheaths in both 
of the last named solutions (V, 12), 130). 
No sheaths appeared upon Spirogyra longata in any strength of 
silver solution here tested, either with (V, 15) or without (V, 14) 
NaOH. Nor were sheaths formed by this species in any strength 
of silver to which was added the undiluted platinum solution (V, 16) 
or inorganic salts to form o. 5 per cent Crone’s solution (V, 17)- In 
these solutions the filaments remained in excellent condition 
throughout the experiments. 
When no swelling became apparent, as in the presence of 
colloidal platinum alone or in that of colloidal platinum and 
colloidal silver together, the cell walls remained uncolored, and 
