a reddish-violet coloration with ferric chloride. Since the coloured 
compound is soluble and easily diffuses through the preparation, the 
ferric chloride-tannin reaction of the globules may also be detected 
when antipyrine is used, and the non-appearance of the reaction in 
the cell-sap may be observed, at least when the ferric chloride acts 
sufficiently rapidly. If the preparations are transferred from the anti¬ 
pyrine- or caffeine solution to a one percent solution of osmic acid, 
the globules are first coloured blue and soon afterwards black, whereas 
the cell sap remains colourless. 
It is evident from the experiments with ferric chloride and with 
osmic acid, that the tannin is completely or almost completely preci¬ 
pitated by a one percent antipyrine solution and by a 0.1 percent 
caffeine solution, for otherwise the cell sap should have shown a 
blue or black coloration. If the antipyrine or caffeine precipitate, 
whether it be a finely divided recent precipitate or one which has 
fused to globules, is dissolved by placing the Spirogyra-M&ments in 
water, and if ferric chloride- or osmic acid solution is then added, 
the cell-sap is coloured blue or black, just as is the case with cells 
which have not been treated with antipyrine- or caffeine solutions. When 
the cells finally die off in antipyrine- or caffeine solution, the globules 
are stained brown; their solubility in water has then decreased, but they 
still give with ferric chloride and osmic acid the reactions referred to. 
By means of comparative experiments with antipyrine- and caffeine 
solutions, and various other tannin reagents, such as potasssium bichro¬ 
mate, osmic acid and ferric salts, with Spirogyra cells containing 
a varying amount, of tannin, I was able to show that the strength of 
the antipyrine- and caffeine precipitates agreed with the strength of 
the precipitates and colorations, given by the above-mentioned reagents. 
For these experiments 1 used Spirogyra filaments, which had been 
centrifuged a few weeks before, and in which there were also all sorts of 
abnormal cells, such as cells without a nucleus, without chromato- 
phores, with several nuclei etc. The tannin content of the cells of 
these filaments varied very much. First the-filaments were treated 
with antipyrine- or caffeine solution and the strength of the precipitate 
in the various cells was noted ; afterwards the filaments were placed 
in water, and when the precipitates had dissolved, they were placed 
m a solution of potassium bichromate, osmic acid or ferric chloride, 
and the intensity of the reaction in the various cells was noted. On 
comparing the various notes it was found that the strength of the 
antipyrine- and caffeine precipitates agreed with the intensity of 
reaction obtained with the other reagents, and therefore corresponded 
to the quantities of tannin present in the various cells. 
