23 
0.1 ‘/, caffeine-solution. At first the precipitates aggregate 
and form globules; gradually their solubility diminishes. 
When the filaments are then transferred into water, the 
globules leave vesicles behind, which have disappeared after 
some days. After a few weeks the globules seem altogether 
insoluble. In dead cells brown globules are found, which 
are also insoluble in water. Neither the globules nor 
their insoluble residues gave even a protein reaction with 
sugar and sulphuric acid, whilst the protoplast became 
distinctly coloured red. On the other hand the globules 
gave tannin reactions. 
It is remarkable that Loew and Bokorny |), who have 
repeatedly insisted on the protein nature of the precipitates, 
assert in one of their latest publications that the colour- 
reactions for protein substances, such as that of Millon 
and the biuret reaction, are not the most important protein 
tests, although they formerly relied on these. Now they 
prefer coagulation by rise of temperature, by alcohol and 
by acids. 
I treated Spirogyra-filaments, with precipitates produced 
by 1 °/, solution of caffeine, by Bokorny's method with 
a saturated caffeine solution containing 20 ‘/, alcohol or 
I exposed the filaments for a short time to the action of 
10 °/, nitric acid or warmed them to 60° in a 1 !/, solution 
of caffeine. In the first two cases [ observed solution, 
in the last case coalescence. The results by no means 
proved the protein nature, as is especially evident from 
the following experiments. 
When I mixed 1 ‘/, solutions of gallnut- or of Spirogyra- 
tannin with an equal quantity of a 1 °/, caffeine-solution 
and heated the mixture to 60° or added 10 !/, nitric acid, 
the precipitate which was formed underwent a modification. 
1) ©. Loew und Th. Bokorny. Aktives Eiweiss und Tannin in 
Pflanzenzellen. l.c. 
