1331 
The views of Loew and Boxorny that precipitates caused in living 
plant-cells by ammoninm carbonate, ammonia, antipyrine, caffeine 
and other basic substances are protein precipitates have been contested 
by Ar Kurercker'), Kiemm ’) and Czarrx ®). All 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 ease of Spirogyra. Here another as yet unknown substance might 
cause the precipitate. 
Czarek states that the precipitates may sometimes take up other 
substanees, such as colouring-matter from the cell-sap and lipoids. 
Also, in spite of the negative results of experimental investigation, 
he thinks that the precipitates sometimes may contain protein sub- 
stances, because the latter occurs in the cells. 
There is a divergence of opinion between the last-mentioned inves- 
tigators as to the place where the precipitates occur. Ar KLERCKER 
holds that they occur in the cell-sap. Kiemm 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 
Bokorny wrongly asserts for the Crassulaceae. On the other hand 
CzarrK believes, that they can occur in the cell-sap and in the eyto- 
plasm as, inter alia, may be the case in the leaf of Echeveria. 
In 1897 an interesting investigation by Overton *) was published. 
He experimented on Spirogyra with ammonia, amines, caffeine, pyri- 
dine, quinoline, piperidine, and alkaloids. He has no doubt at all 
that the precipitates which are found in the cell-sap are compounds 
of tannin with the above substances. He describes in detail the 
phenomena which are brought about by solutions of caffeine of 
different strength, namely, when successively stronger or weaker 
solutions are added. In explanation it is said that the compound of 
tannin and caffeine are in a condition of hydrolytic dissociation. 
1) J. E. fF. ar KLERCKER, Studien über die Gerbstoffvakuolen. Inaug. Diss 
Tübingen 1888. 
2) P. KremM, Beitrag zur Erforschung der Aggregationsvorgänge in lebenden 
Pflanzenzellen. Flora 1892, p. 355. —Ueber die Aggregationsvorgänge in Crassulaceen- 
zellen Berichte d d. bot. Gesellsch. Bd. X. 1892, p. 237. _— 
8) KF. Czapegr, Ueber Fiillungsreaktionen in lebenden Pflanzenzellen und einige 
Anwendungen derselben. Ber. d.d. bot. Gesellsch. Bd. XXVIII. 1910. Heft V. p. 147. 
4) EK. Overton, Ueber die osmotischen Eigenschaften der Zellen in ihrer Be- 
deutung fiir die Toxikologie und Pharmakologie. Zeitschr. f. Physikal Chemie XXII. 
Bd, 1697; p. 189: 
