592 RECORD OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



A. GENERAL, including Embryology and Histology 

 of the Phanerogamia. 



Permeability of Pellicle Precipitates.* — The well-known experi- 

 ments of Traube on artificial cells have been repeated by Hugo de 

 Vries, who comes to conclusions quite opposite to those of the German 

 observer. 



Starting with Traube's experiments upon the artificial cell or 

 pellicle-precipitate produced by a copper salt in a solution of potassium 

 ferrocyauide, De Vries says that if, as Traube maintains, the precipi- 

 tated membrane is impermeable to its two membranogens (i.e. the 

 copper salt and the ferrocyanide), the membrane will not undergo any 

 increase in thickness ; while if, on the other hand, the pellicle is 

 permeable by the membranogens, it will continually increase in thick- 

 ness until one of them is exhausted. 



De Vries experimented upon a flaccid cell of cojiper ferrocyanide, 

 obtained by introducing a drop of a 3 to 5 per cent, solution of cupric 

 chloride, by means of a fine pipette, into the bottom of a tall vessel 

 containing a 20 per cent, solution of potassium ferrocyanifl6. The blue 

 drop became sui'rounded with a delicate, colourless, transparent pel- 

 licle, which for a half to one hour seemed to undergo no change. At 

 the end of this time, however, brownish spots appeared on it, and 

 increased in number and size until the whole cell-wall had a brown 

 tint, which gradually darkened, until the whole pellicle was dark 

 brown, opaque, and quite rigid and brittle. During the whole time 

 — at the end of twenty-fuur hours, in fact— the cell had undergone no 

 increase in size. If ruptured at this time, the rent was not closed up 

 by the formation of a new pellicle, showing that all the copper salt 

 had passed out of the cell ; moreover, the colour of the contents of the 

 latter was seen to be yellow — that is, to consist of the ferrocyanide. 



Thus, the pellicle of cupric ferrocyanid is proved to increase in 

 thickness, and must therefore be permeable to one or both of the 

 membranogens. Several other experiments of similar nature were 

 made, and all tended to prove the same thing — in all there was a 

 progressive increase in the thickness of the pellicle, and a continual 

 change in its physical properties. 



The author concludes by remarking that, by these results, the 

 supposed analogy between pellicle-precipitates and living protoplasm 

 is shown to be only apparent, and devoid of all real significance."]" 



Origin of Chlorophyll-grains. — The view of Mohl, Sachs, Wiesner, 

 and others, that grains of chlorophyll are formed directly from the 

 starch and other carbohydrates which constitute the reserve food- 



* 'Arch. Neerland.,' xiii. (1878) p. 344. 



t This remark can hardly be said to apply to Traube's experiments "with 

 gelatin-taunate pellicles, althongli the fact of the copper-ferrocyanide pellicle 

 growing by deposition of layers, and not, as Traube thought, by intussusception, 

 renders a repetition of these experiments necessary. (See Sachs' ' Textbook of 

 Botany,' p. 594.) 



