LIFE OF THE PLANT-CELL. 107 



I. General Modifications of the Life of Cells in consequence of the 

 Association of several Cells. 



51. As soon as a large number of cells are united into a cel- 

 lular tissue, part of them at least are shut out from immediate 

 contact with the nutritive fluid ; consequently, they receive nutri- 

 ment by endosmosis only from the contiguous cells, in which, 

 however, the fluid has always already undergone a change. 



When all the cells of a tissue contain a fluid of equal density, en- 

 dosmosis takes place in those which are in immediate contact with water, 

 in consequence of which the fluid contained in them is diluted, and there 

 is established between them and the next cells a condition of the fluids fa- 

 vourable to endosmosis, and so on. This is the most important relation in 

 which cell-life can be viewed, because the sole, universal motion of the 

 fluids, upon which the nutrition of the whole plant is contingent, arises 

 therefrom. There are absolutely no vessels for the distribution of the 

 nutritive fluid in the body of plants ; and no person would take the 

 trouble of looking for them, or would imagine he saw them anywhere, 

 but one who goes to the investigation of plants labouring under the 

 false and pernicious prejudice in favour of the supposed unhappy ana- 

 logy between them and animals ( 63 146.). The sound sense of 

 all botanists has been much confused on this subject ; who have ad- 

 vanced every possible perversion of physics and logic, rather than part 

 with this fixed idea.* Every living cell, however, which obtains fluid by 

 endosmosis immediately induces in such fluid a chemical change and con- 

 verts it into assimilated matter, so that the cells which are remote 

 from the source of the raw nutritive fluid do not receive it in this state. 

 In them, consequently, there is no occasion for the process of assimilation 

 to go on, as far as relates to the decomposition of water and the fixation 

 of carbonic acid ; they enjoy, however, an active life, are nourished, form 

 new cells, &c., as in the woody bundles of dicotyledons. This is suffi- 

 cient to show how untenable is the law instituted by Liebig/f 



52. By the arrangement of a great mass of the cells in a 

 plant, some of them are partially brought into contact with the 

 atmospheric air. From this, two important conditions result : first, 

 that the water evaporates constantly from the surface of the cell 

 in proportion to the warmth, dryness, and motion of the air, un- 

 less the cells are protected in some special manner ( 69.); in 

 consequence of this evaporation the fluid in the interior of the 

 cell is continually lessened in bulk and concentrated, and thus the 

 endosmosis towards the other cells is strengthened and sustained : 

 secondly, that the fluid contained in the cells is enabled to absorb 

 gases from the air, viz. carbonic acid and ammonia, and occasionally 

 oxygen. 



* See Knight, in Treviranus's Beitrage zur Pflanzenphysiologie, Gottingen, 1811, 

 p. 162. Sennebier, Physiologic vegetale, vol. ii. cap. iv. p. 332. ; and others. 



f " No material can be regarded as the nutriment of plants whose composition is/ 

 identical with or similar to their own, and consequently the assimilation of which can 

 ensue without the separation of oxygen." Lieb. Org. Chem. p. 26. The law is at 

 once simply contradicted by the great number of Fungi and true parasites. 



