On intravital precipitates

The precipitates caused by basic substances in living plant cells have long attracted the attention of investigators and the literature on this subject is already voluminous. Charles Darwin was the first to investigate these precipitates. He ] ) first mentions the phenomenon in his work on insectivorous plants, and calls it aggregation. As de Vries2) has pointed out, Darwin includes two different phenomena under this name: in the first place, the movements which he discovered in the protoplasm of the cells of the glands of Drosera rotundifolia and other insectivorous plants, movements which occur whenever stimulation causes an increased secretion, and in the second place the precipitates which occur in the protoplasm when ammonium carbonate is used as a stimulus. As Ch. Darwin 3) has shown, precipitates with ammonium carbonate and with ammonia are also formed in many other cases in living plant cells. He stated that the precipitates no longer occur when the preparations are heated in water for 2 to 3 minutes to the boiling point and on this account he was inclined to consider the 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 I 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.