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coloured violet by means of an iodine solution such as 
iodine in potassium iodide. Of course care must be taken 
that the violet colour is not masked by the addition of 
much iodine. In chemical books I have found no mention 
of a precipitate. 
When hide-powder or pieces of egg-white are brought 
into contact with a tannin solution, washed with water 
after some time and then treated with iodine in potassium 
iodide solution, they usually show a dirty brown colour; 
after repeated washing with water a fine violet colour 
(KI et V. 591, 596) appears, however. 
This reaction can also be applied to Spirogyra, but in 
this case the tannin solution isunnecessary, because Spirogyra 
itself contains tannin in solution in its cell-sap. The filaments 
of Spirogyra are warmed to 60° in water. They are then 
killed, the tannin leaves the vacuole and partly combines 
with the protein ot the protoplast. If the filaments are now 
treated with iodine in potassium iodide solution and after- 
wards washed with distilled water until the iodine reaction 
of the starch disappears, it is then found that those parts 
of the protoplast which are rich in protein, are coloured 
violet. The nuclei with the nucleoli are finely coloured, the 
pyrenoids more faintly. 
I have been no more able to find protein in the intravital 
precipitates with caffeine, antipyrine and ammonium car- 
bonate than were Af Klercker, Klemm and Czapek:; 
neither when te precipitates with caffeine and antipyrine 
had been treated according to Bokorny's !) method with 
1/,,%/, ammonia and had thus become insoluble. 
Nor have I been able to obtain a protein reaction when 
the precipitates were some weeks old and had become 
insoluble. Spirogyra can, it should be noted, remain alive 
for several weeks in a 1 °/, antipyrine-solution and in a 
1) Th. Bokorny, Zur Kenntnis des Cytoplasmas. L.c. p. 106. 
