492 ORGANOLOGY. 



In all future experiments, it will be most important to bear in mind 

 that each cell carries on its own existence, and that, therefore, what holds 

 good for one cell does not necessarily apply to others. No cells, with 

 the exception of some root-cells, feed upon absolutely raw material, as it 

 is received from the earth ; they live upon matter more or less assimilated, 

 upon fluids that contain albumen (or the like), dextrin, grape sugar, and 

 organic acids, but in which gum is probably never present, and cane 

 sugar only in rare cases. Every individual which, as branch, bud, or 

 embryo, still stands in connection with the mother plant when separated 

 from the original plant, cannot continue to live on organic matter, and 

 perishes unless it can appropriate inorganic matter by the formation of 

 root-cells. All conclusions founded upon leaves, or other parts of the 

 plant which have been separated from its entire body, are inadmissible as 

 applied to the entire plant. 



1 93. For the perfect nutrition of plants, not only is the absorp- 

 tion of the organic elements and the sulphur and phosphorus found 

 in combination with the nitrogenous substances requisite, but also 

 the inorganic salts which they contain. All plants that have 

 hitherto been burned, with the exception of the mother of vinegar, 

 have been found to leave behind them an ash, which must have 

 been taken up by the plant. These substances must be regarded 

 as essential to the nourishment of plants, though as yet we 

 do not understand in what consists their importance. We may, 

 with Liebig, arrange plants or their organs into four classes, ac- 

 cording to the predominating elements left in the ashes (when 

 above 50 per cent.): 



Alkaline plants : succulent, containing meal and sugar. 



Chalk plants ; Dicotyledons, leaves, fruits, and stalks. 



Siliceous plants : Monocotyledons, leaves and stalks. 



Phosphatic plants : Plants abounding in nitrogen, seeds. 



The investigations which have hitherto been made respecting the inor- 

 ganic elements of plants, are much too recent, too inconsiderable, and too 

 inaccurate to permit us to draw conclusions from them with regard to the 

 process of nutrition in plants. It appears, however, to be established, 

 that for every species (and variety) certain. different kinds and qualities 

 of matter are found so constant, that we may regard them as essential 

 elements for those plants without which their vegetation and their nutri- 

 tion would be impossible, and that they must, therefore, be offered these 

 in the form of food. We may even maintain that the specific varieties of 

 plants, so far as their nutritive processes are concerned, depend almost 

 exclusively upon the inorganic elements, whilst the organic elements re- 

 quisite to all plants are alike or nearly alike for all. 



When, however, we find all parts of plants which are rich in com- 

 pounds of the dextrin series abounding also in potassa and soda, and all 

 organs which contain much of the protein compounds containing also 

 almost in equal measure salts of phosphoric acid, we must arrive at 

 the conclusion, that the alkalies have, with the chemical processes of 

 the dextrin series, and the salts of phosphoric acid, with the origin of 

 the protein compounds, a close and essential connection. It further 

 appears that the solidity of the cell walls depends in part upon the in- 

 organic matter received by the plant and deposited in the substance ; 



