ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1017 



take in sap at one side and let it flow out at the other, solely in virtue 

 of its intracellular turgescence. Godlewski criticizes Sachs's con- 

 clusion aucl illustrative experiments, and finds himself forced to 

 conclude that the osmotic turgescence is not enough, aud to admit a 

 special, very pronounced action of the living protoplasm. 



If a parenchymatous cell has sucked in osmotically a certain 

 quantity of water, the elimination of this water without the substances 

 in solution may occur in two ways, either (1) by increase of pressure 

 from the walls on the cell-sap, or (2) by a diminution of the attraction 

 between the water and the cell-contents. (1) Godlewski supposes 

 that when the turgescence of a cell has attained a certain degree, the 

 laj-er of protoplasm lining the walls has become more permeable to 

 water at the place where it is in contact with fibre or vessel ; and 

 that, at the same time, the whole protoplasm contracts in consequence 

 of (unknown) forces liberated in respiration. (2) Different sub- 

 stances attract water in very different degrees. If cane sugar in the 

 cell be inverted, the cell's attraction for water doubles, and vice versa. 

 But such transformations really occur; and it is in this action of the 

 living protoplasm that the author finds the source of force sufficient 

 to cause the water to mount up the fibres and vessels. He proceeds 

 to apply his theory concretely to the stem of Coniferte. 



The hypotheses on which Godlewski's theory rests are (1) that 

 periodic changes in the disposition of the molecules of the protoplasm 

 may make the latter more permeable to water at a certain time, and 

 at a definite place ; (2) that periodic changes occur in the turgescence 

 of the cell, excited by periodic contractions of the protoplasm, or 

 periodic changes in the chemical composition of the cell-contents. 



Movement of Water in Wood.* — Herr M. Scheit propounds the 

 theory that, in addition to the ordinary movement of water in wood, 

 there is also a movement of water in the gaseous form, a movement 

 of distillation. The former he regards as being occasioned exclusively 

 by root-pressure. The distillation movement begins as soon as the 

 cavities of the cells and vessels are no longer completely filled with 

 water ; and it can only take place when the temperature of the plant 

 decreases upwards, which may result from the low conducting powers 

 of the wood and soil connected with the loss of heat occasioned by 

 transpiration. The vessels are the chief channels of the distillation- 

 movement, while the tracheitis serve especially for the condensation of 

 the aqueous vapour. 



Transpiration-stream in cut branches f — Prof. F. Darwin and 

 Mr. E. W. Pliillips have repeated Dufour's experiments on the effect 

 on transpiration of two opposite incisions in a branch. They find a 

 general difference in the results between Angiosperms and Gymno- 

 sperms, the former represented by Helianthus, the latter by Taxus. 

 In the former case transpiration is reduced to a minimum ; in the 



* Jenaisch. Zeitschr. f. NaturwLss., xix. (1SS5) pp. 678-734. See Bot. 

 Gentralbl., xxvi. (1886) p. 294. Gf. tiiis Journal, v. (1885) p. 679; cude, p. 283. 

 t Proc. Cambridge Phil. Soc, v. (1886) pp. 330-67 (1 pi.). 



