PROTOPLASM. 



27 



K 



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of the protoplasm, 1 as, for instance, a solution of common salt, 

 the protoplasm separates from the cell-wall, and by its con- 

 traction shows clearly that it is a 

 closed sac. At a later stage 

 in some cells even this thin 

 protoplasmic sac wholly dis 

 appears. 



121. Protoplasm itself must 

 be regarded as essentially 

 transparent and colorless, but 

 it is seldom found without 

 some admixture of other mat- 

 ters, which give it a granular 

 appearance. The granules 

 are generally very small, and 

 as a rule are not found at the 

 peripheiy of the mass. The 

 limiting surface of the proto- 

 plasmic mass is further dis- 

 tinguished by being somewhat denser and firmer than the sub- 

 stance it encloses ; and although it cannot be separated from 

 the latter by mechanical means, it is often spoken of as a film ; 2 



which take up the coloring matter readily, leaving the remainder of the mass 

 unstained. It is believed by Schmitz that the unstained mass is a homoge- 

 neous liquid filling the meshes (Sitzungsber. der niederrhein. Gesellschaft in 

 Bonn, 1880). 



1 Such substances are termed plasmolytic agents. 



2 Of the appearance of protoplasm, the following remarks by Mohl, who first 

 gave it the nnme in 1846, are of interest. " If a tissue composed of young cells 

 be left some time in alcohol, or treated with nitric or muriatic acid, a very 

 thin, finely granular membrane becomes detached from the inside of the wall 

 of the cell in the form of a closed vesicle, which becomes more or less con- 

 tracted, and consequently removes all the contents of the cell, which are 

 enclosed in this vesicle, from the wall of the cell. Reasons hereafter to be 

 discussed have led me to call this inner cell the pri'ni<>r<li<<l utricle. ... In 

 the centre of the young cell, with rare exceptions, lies the so-called nucleus 

 celliilce of Robert Brown. . . . The remainder of the cell is more or less 

 densely filled with an opaque, viscid fluid of a white colour, having granules 

 intermingled in it, which fluid I call protoplasm " (Mohl: The Vegetable Cell, 

 Ib-nfrey's Translation, 1852, pp. 36, 37). 



FIG. 1. From developing anther of Orchis maculata, showing young cells com- 

 pletely filled with protoplasm. Observe also the nucleus with its nucleolus, in each 

 cell. (Guignard.) 



FIG. 2. A hair from the stamen of Tradescantia pilosa, showing the protoplasm in 

 the form of granular threads running from side to side of the cell-cavity. The white 

 spaces between these threads are vacuoles. The nucleus can also be seen in each of the 

 four cells. (Jacobs.) 



