210 PROTOPLASM. 



jjrotoplasm of the cells of Tradescantia stamen-hairs is exhibit- 

 ing rapid circulation, cause an increase in the rate of movement. 

 This fact has been considered to show, in connection with the 

 eases mentioned, that for the most rapid circulation of proto- 

 plasm there must be a definite amount of water, — the optimum. 



580. When any of these plasmolytic agents are used in too 

 concentrated a solution they may exert a much more marked 

 effect upon the protoplasmic contents of a cell ; not only does 

 all movement cease, but the mass shrinks into small bulk, and 

 does not afterwards recover its former shape and size. As a 

 result of their action, two other phenomena are presented : (1) the 

 protoplasm of one cell can be seen in some cases to be connected 

 through the cell-wall with the protoplasm in the adjoining cell ; 

 (2) a change takes place in the firmness or turgor of the cell- 

 wall. Both of these phenomena must receive attention at a later 

 stage. When a cell containing living protoplasm is placed in a 

 harmless and dilute solution of an^- coloring-matter, for instance 

 logwood, its wall becomes more or less tinged by the dj-e, but 

 the protoplasm retains for a while at least its power of move- 

 ment, and does not take up any of the dye. If, however, the 

 protoplasmic mass is injured or dead, it absorbs the coloring- 

 matter with great avidity. 



581. Belations of protoplasm to various gases. Experiments 

 upon the effects of gases on the behavior of protoplasm can 

 be best conducted by means of the simple gas-chamber shown 

 in Fig. 195. A current of the gas employed is drawn through 

 the tube a by means of anj- simple aspirator ; and in a few 

 seconds the specimen previously placed upon the glass at 5, 

 and protected by a cover-glass, is thoroughly surrounded by 

 it. By the use of this apparatus it has been found that the 

 presence of free oxygen is essential to protoplasmic movements. 

 Hofmeister and Kiihne have shown that when this gas is no 

 longer supplied to the protoplasmic mass or to the cells in 

 which the protoplasm is contained, all movements cease. Thus 

 Hofmeister' found that the circulation of Nitella was completely 

 arrested in thirteen minutes after the air was wholly removed. 

 Kuhne^ replaced by hjdrogen the air in which the hairs of 

 Tradescantia had shown rapid movement, and after several 

 hours all motion was arrested. 



582. Corti," the discoverer of the circulation in Nitella, placed 



1 Die Lehre von der Pflanzenzelle, p. 49. 

 ^ Untersucluingen liber das Protoplasma, 1864, p. 107. 

 ' Meyen : Pfliinzenpliysiologie, ii. 224. 



