38 



oxalic acid the nucleus of Spirogyra orbicularis was observed to swell 

 up, frequently to six times its normal volume, and become turbid and 

 opaque, while the cytoplasm still remained alive for some time. In 

 coDcentrated solutions the cells die too quickly to show such character- 

 istic symptoms, their death being due chiefly in this case to mere 

 acidity. 



When some lilaments of Spirogyra majuscula were placed in 500 cc. of a 

 solution of free oxalic acid^ in even as high dilution as 0.0001 per cent, 

 the writer observed great injury to some of the threads after live days. 

 In most of the cells the plasma strings were retracted, the nucleus was 

 contracted and rolled to the cell wall, and the sinuate margins of the 

 chlorophyll bands were swollen up and numerous little drops became 

 visible in them.^ A very striking feature was the long-continued per- 

 sistence of the turgor under these conditions, this being due to the 

 cytoplasm remaining alive for a considerable time. In equally diluted 

 solutions of tartaric acid most of the cells were perfectly normal after 

 nine days, which shows that the character of acidity at this high dilu- 

 tion exerted merely a secondary influence, and that this alone can not 

 account for the action of the highly diluted oxalic acid. 



FORMATION OF LIME INCRUSTATIONS. 



It may not be out of place here to say a few words about the forma- 

 tion of incrustations of calcium carbonate on certain aquatic plants, 

 especially Chara — a x)henomenon which Pringsheim^ tries to explain on 

 the hypothesis that by assimilation of the dissolved carbonic acid the 

 nentral calcium carbonate is produced from the bicarbonate. However, 

 the fact that not every plant growing in the same water and near 

 Chara shows the incrustation must lead to the assumption tbat either 

 the assimilation is of much greater energy in Chara than in many other 

 plants, or that the surface of this plant is especially adapted for the 

 absorption of the neutral calcium carbonate. 



Hassack"^ advanced another hypothesis, that is, that the plants 

 secrete an alkaline carbonate, which decomposes the calcium bicarbon- 

 ate. However, the writer has proved this view to be entirely erro- 

 neous.'' The reaction with phenol phthalein, which Hassack used 

 is not due to an alkaline carbonate, but to neutral calcium carbonate 

 in a colloidal condition. Even the warming of ordinary water rich in 

 calcium carbonate will produce ephemerally a red color with phenol- 

 I)hthalein. 



^Purest water distilled from glass vessels was used for all experiments with 

 Spirofjyra. 



2 Considerable swelling of the nucleus took place in a solution of 0.01 per cent 

 oxalic acid. 



3 Jahrb. f. Wiss. Bot. , Vol. XIX, p. 138. 



" Unters. aus d. Bot. Instit. Tubingen, Vol. II, pp. 469-475. 

 5 Flora, 1893, No. 4. 



