15 
reaction as a vital one. With regard to the chemical 
nature and physiological significance of the substance of 
which the precipitates are composed, Darwin expressed 
himself very cautiously. He supposed that they consist 
of protein and considered that we have to deal with an 
excretion product. He concluded his last-mentioned paper 
as follows: “But I hope that some one, better fitted than 
Ï am, from possessing much more chemical and histological 
knowledge, may be induced to investigate the whole 
subject”. From this it follows that Darwin may have 
thought that another explanation of the phenomenon he 
had discovered was also possible. 
Fr. Darwin!) defends his father's views, as far as the 
chemical nature of the precipitate is concerned, which 
ammonium carbonate produces in the tentacles of Drosera 
rotundifolia. De Vries *) is also of the opinion that the 
precipitate belongs to the group of the proteins, as far 
as its behaviour towards reagents is concerned. 
The precipitates caused by ammonium carbonate in the 
cell-sap of Spirogyra and of other plants, have also been 
investigated by Pfeffer *). In his opinion they are com- 
posed of protein tannate and give reactions both with 
protein- and with tannin-reagents. 
Loew and Bokorny ‘) have written numerous papers 
1) Francis Darwin, The process of aggregation in the tentacles of 
Drosera rotundifolia. Quarterly journal of microsc. science. Vol. XVI. 
1876, p. 300. 
DIE pa42-fiandi sfr 
3) VW. Pfeffer, Ueber Aufnahme von Anilinfarben in lebenden Zellen. 
Untersuchungen aus dem botan. Institut zu Tübingen. 2. Bd. 1886— 
1888. p. 239 ff. 
#) ©. Loew und Th. Bokorny, Ueber das Vorkommen von acti- 
vem ÀAlbumin im Zellsaft und dessen Ausscheidung in Kôrnchen durch 
Basen. Bot. Zeit. 45. Jahrg. 1887. p. 849. — Ueber das Verhalten von 
Pflanzenzellen zu stark verdünnter alkalischer Silberlôsung. Bot. Cen- 
tralblatt. 10. Jahrg. 1889. XXXVIIL Bd. p. 581 and 614. XXXIX. Bd. 
