THE PLANT-CELL. 25 



belongs the substance (or mixture of substances) to which 

 Reinke has given the name of plastin ; to the first belong 

 the proteids termed globulins (Hoppe-Seyler), which are also 

 soluble in solutions of common salt, and the peptones, which 

 are also soluble in water and are not precipitated from their 

 solution on boiling. These proteids all consist of Carbon, 

 Hydrogen, Nitrogen, Oxygen, and Sulphur, and, according to 

 Reinke, plastin contains Phosphorus in addition. 



Reinke studied the composition and properties of plastin obtained 

 from the plasmodium of ^Ethalium, a myxomycetous Fungus. The pro- 

 bable presence of phosphorus in its molecule is of interest, in that it 

 suggests a relation between the plastin of the protoplasm and the nuclein 

 (see infra] of the nucleus. Globulins have been obtained by Hoppe- 

 Seyler from buds and young shoots of plants, and they are especially 

 abundant in seeds. Peptones have not been found in quantity in any 

 parts excepting seeds, in which they are always present and are usually 

 abundant. 



This chemical analysis of the protoplasm in the cell 

 throws some light also upon the physiological relation of the 

 various proteids to each other. We find that whereas in a 

 young growing cell the quantity of proteids present is con- 

 siderable, it gradually diminishes as the cell grows older, 

 until, when the cell has ceased to grow, the protoplasm con- 

 sists of little more than the plastin-framework. The cell 

 shewn in fig. 3 ha's reached this stage. It appears probable, 

 therefore, that the plastin-framework is the actual living proto- 

 plasm, the organised proteid of the -cell, whereas the globulins 

 (and peptones, if present) are dead or unorganised proteid, 

 the enchylema of Hanstein. Reinke found in his researches 

 on ^Ethalium that the unorganised proteid could be ex- 

 tracted from the plasmodium by simply squeezing it. A 

 mechanical analysis of this kind takes place in the ripening 

 of seeds. In a cell of a ripe seed it is found that the glo- 

 bulins and peptones are deposited in the form of granules 

 (aleurone-grains) in the meshes of the plastin-framework. 



In addition to the protoplasm, as described above, the 

 cells of the higher plants commonly contain differentiated 

 protoplasmic bodies, which may contain a colouring matter 



