7 
The views of Loew and Bokorny that precipitates 
caused in living plant-cells by ammonium carbonate, am- 
monia, antipyrine, caffeine and other basic substances are 
protein precipitates have been contested by Af Klercker!}), 
Klemm”*) and Czapek*). AI! these consider that the 
precipitates are in reality tannin precipitates. On treating 
these and the cell-sap with protein reagents they always 
obtained negative results, while on the other hand tannin 
reagents gave positive ones. 
It is worthy of notice that Klemm in connection with 
his experiments with methylene-blue regards tannin as of 
secondary importance in the case of Spirogyra. Here 
another as yet unknown substance might cause the pre- 
cipitate. 
Czapek states that the precipitates may sometimes take 
up other substances, such as colouring-matter from the 
cell-sap and lipoids. Also, in spite of the negative results 
of experimental investigation, he thinks that the precipi- 
tates sometimes may contain protein substances, because 
the latter occurs in the cells. 
There is a divergence of opinion between the last- 
mentioned investigators as to the place where the preci- 
pitates occur. Af Klercker holds that they occur in the 
cell-sap. Klemm thinks that detailed study will probably 
show more and more, that they are formed exclusively 
in the cell-sap and not in the protoplasm or in both, as 
1) J. E. F. Af Klercker, Studien über die Gerbstoffvakuolen. Inaug. 
Diss. Tübingen 1888. 
=) P. Klemm, Beitrag zur Erforschung der Aggregationsvorgänge 
in lebenden Pflanzenzellen. Flora 1892, p. 395. — Ueber die Aggre- 
gationsvorgänge in Crassulaceenzellen. Berichte d. d. bot. Gesellsch. 
Bd: X°11892; p. 237: 
#) EF. Czapek, Ueber Fällungsreaktionen in lebenden Pflanzenzellen 
und einige Anwendungen derselben. Ber. d.d. bot. Gesellsch. Bd. XX VIII. 
1910. Heft V, p. 147. 
Recueil des trav. bot. Néerl. Vol. XI. 1913. 2 
