THE MICROSCOPE IN HISTOLOGY AND BOTANY. 129 



especially in the Volvox, and some have considered it 

 probable that an organism may live a truly vegetable life 

 at one period and a truly animal life at another. 



Analogous to amoeboid movements, is the motion of 

 bioplasmic fluid in the interior of undoubtedly vegetable 

 cells. This movement is called cydosis, and may be de- 

 tected under the microscope by the granules or particles, 

 which the current carries with it in the transparent cells 

 of Chara,VaUisneria, etc., and in the epidermic hairs of 

 many plants, as Tradescantia, Plantago, etc. (Plate VI r 

 Pig. 91). 



The bioplasm of plants may be stained with carmine 

 solution without affecting the cell- wall or other formed, 

 material. 



Cell-wall or Membrane. Plants, whether simple or 

 complicated in structure, are but cells or aggregations of 

 cells. In the simplest vegetables or Protophytes, each cell 

 lives as it were an independent life, performing every 

 function; while in the higher plants, as the palm or oak, 

 the cells undergo special modifications, and serve various 

 functions subsidiary to the life of the plant as a whole. 



Cell-membrane, or the envelope of formed material, was 

 formerly thought to be composed of two layers, to the 

 inner one of which the name of primordial utricle was 

 given, but this is now considered to be but the external 

 surface of the bioplasm or germinal matter. 



The chemical nature of cell-membrane is nearly identi- 

 cal with starch, being composed of cellulose. The presence 

 of cellulose may be shown by the blue color which is 

 produced by applying iodine and sulphuric acid, or the 

 iodized solution of chloride of zinc. 



Endosmose will take place in cell-membrane, allowing 

 solutions to pass through, as pabulum, and the manner of 

 this passage may in some instances determine the subse- 

 quent deposit of formed material. Sometimes actual pores 

 are left in the membrane, as in Sphagnum (Plate YI, Fig. 



9 



