25 
carefully heated above a micro-flame, the cells are succes- 
sively killed. The tannin passes through the protoplasmic 
layer and cell-wall and forms a precipitate in the egg- 
white-, gelatin- or glue-solution. On careful heating the 
precipitate lies immediately against the Spirogyra-filament. 
The cells which are still alive are not surrounded by a 
precipitate. It can be established by using solutions of 
ferric salts, and other tannin reagents, that the precipi- 
tate formed outside the filament is a tannin precipitate. 
When Spirogyra has been slowly heated in water to 
60° in a test-tube placed in a water-bath, it dies. In this 
case much tannin usually combines with the protein present 
in the protoplast and only a little leaves the cell. When 
a large quantity of Spirogyra was heated to 60° in very 
little water, the liquid sometimes gave after filtration only 
a very weak tannin reaction with ferric salts, whilst the 
nuclei and pyrenoids always gave a distinct reaction. The 
nuclei and pyrenoids also gave a distinct tannin reaction 
with iodine in potassium iodide solution. When sufficiently 
washed out with water they show a fine red violet coloration. 
When starting with dead material, it is desired to 
produce with antipyrine, caffeine and other basic substances 
precipitates which agree with those occurring in living 
cells, the following method may be adopted. À number 
of Spirogyra-filaments are taken, washed out with distilled 
water, which is allowed to drip off as much as possible 
and then they are heated to 60, dried as well as possible 
by means of gentle pressure between filter-paper, and 
extracted 2 or 3 times with a mixture of 4 parts of ether 
and 1 part of alcohol, such as is used in the extraction 
of tannin from gallnuts; the fluid obtained is filtered and 
evaporated in a vacuum. The residue, which resembles 
gallnut-tannin, is dissolved in a little distilled water and 
filtered. We thus obtain a solution, which gives all the 
possible tannin reactions, with ferric salts, potassium bichro- 
