Shortly before the appearance of CzaPEK’s publication quoted above 
1‘) made a preliminary communication on the demonstration of 
tannin in the living plant and on its physiological significance. While 
searching for a method of studying the physiological significance of 
tannin in Spirogyra my attention was also drawn to antipyrine and 
caffeine, substances which bad not then been used for that purpose. 
Like Overton I described the precipitates as tannin precipitates 
and have never for a moment thought of regarding them as protein 
precipitates. All the results were in agreement with the view that 
they were tannin precipitates. In the paper referred to above I drew 
attention to the fact that they were earlier described erroneously by 
Loew and Bokorny?} as protein precipitates. To this these authors *) 
soon replied. 
In connection with the various views on the chemical nature of 
intravital precipitates, I have further considered whether protein 
might occur in them and subsequently performed some experiments on 
Spirogyra maxima (Hass.) Wittr. which in my opinion render much 
more certain the view that the precipitates contain no protein, than 
was already the case. It follows moreover from these experiments 
that the precipitates occur in the cell-sap and not in the cytoplasm. 
I will first explain this point. | 
Boxorny*) assumes that in Spirogyra proteosomes are formed in 
the cytoplasm as well as in the cell-sap. He thinks he has furnished 
proof of this by combining the formation of proteosomes with abnormal 
plasmolysis. 
He placed Spirogyra in a mixture of equal parts of a 10°/, solution 
of potassium nitrate and a 0.1°/, solution of caffeine. After the action 
proteosomes were observed in the cytoplasm as well as in the con- 
tracted vacuole. KrrmM*) agrees with Boxorny with respect to the 
localisation of the precipitate in Spirogyra. Kiem first allowed the 
precipitate to occur and then to be plasmolysed. 
When Bokorny*) first brought about abnormal plasmolysis with a 
1) C. van WISSELINGH, Over het aantoonen van looistof in de levende plant 
en over hare physiologische beteekenis. Verslagen der Koninkl. Akad. van Weten- 
schappen te Amsterdam, Maart 1910. On the tests for tannin in the living plant 
and on the physiological significance of tannin. These Proc XII, p. 685. 
2) O. Loew and Tu. Boxorny, Aktives Eiweiss und Tannin in Pflanzenzellen. l.c. 
3) TH. BoKorNy, Neue Untersuchungen über den Vorgang der Silberabscheidung 
durch actives Albumin. l.c. p. 206. 
4) P. KremM, Beitrag zur Erforschung der Aggregationsvorgänge in lebenden 
Pflanzenzellen. 1. e. p. 407. 
5) Tu. Boxorny, Ueber die Einwirkung basischer Stoffe auf das lebende Proto- 
plasma. |. c. p. 209. 
