32 
there in soluble condition in the alveolar fluid. When the 
protein-solution and the cell-sap containing tannin come 
into contact with each other, the above mentioned preci- 
pitates are formed, from which it follows, in my opinion, 
that in addition to tannin protein in solution cannot be 
present in the cell-sap. They would at once form an 
insoluble compound with each other. It is thus impossible 
that, as Loew and Bokorny assume, the precipitates, 
which are formed in the cell-sap by basic substances, are 
protein-precipitates or, as Pfeffer assumes, precipitates 
of protein and tannin. 
In reality they are tannin precipitates. Although the 
possibility is not excluded that other substances are some- 
times present in small quantity, experimental investigation 
yields the proof, that there can be absolutely no thought 
of protein-substances in the first place, 
Tannin and protein are separated in the living cells in 
a remarkable manner. Tannin in solution occurs in the 
cell-sap; proteins can be demonstrated in the nucleus, the 
chromatophores and the cytoplasm. They are either solid, 
as for example, the pyrenoids of the chromatophores or 
dissolved, as in the cytoplasm. The nucleoli which contain 
a viscous substance, in which the two nucleolus-threads 
lie !) give specially clear protein-reactions. 
There still remains the question why a solution of 
ammonium-Carbonate which causes a precipitate in the 
cell-sap of Spirogyra, may be much more dilute than that 
which produces a precipitate in a solution of gallnut- 
tannin or of Spirogyra-tannin. 
It is obvious that in the water in which Spirogyra 
grows and also in the cell-sap salts are present and I 
have on this account traced the influence of various salts 
1) C. van Wissclingh, Ueber den Nucleolus von Spirogyra. Bot. 
Zeit. 1898, p. 202. — Ueber abnormale Kernteilung, I. c. 1903, p. 217. 
