CHANGES OF MOLECULAR STRUCTURE, DUE TO SWELLING 83 



Other Peculiarities. It might be expected that the physical properties and 

 powers of conduction of organized bodies should be different in the three planes 

 intersecting at right angles, and the little that is known on this point supports this 

 conclusion. The properties of elasticity and rigidity, the conduction of sound 1 , 

 heat, and electricity, have not as yet been investigated in connexion with the 

 molecular structure of organized bodies. The general phenomena connected with 

 elasticity, tissue tensions, heat, light, and electricity will be dealt with later. In 

 this connexion Ambronn's investigations are of great interest 2 , for he has shown 

 that gelatine plates, in which anisotropy has been induced by tensions set up 

 whilst drying, orientate themselves in magnetic and electric fields, just like aniso- 

 tropous crystals. 



SECTION 14. Changes of Molecular Structure due to Swelling. 



In the vital mechanism, constructive and destructive processes are always 

 taking place, as well as a variety of intermediate changes, by which the pro- 

 perties of the protoplast and of its organs may be more or less modified to 

 suit the economy of the whole. Thus in the case of a cell-wall, the modi- 

 fications it may undergo, leading to the formation of cork cuticle or wood, 

 are of the utmost importance in the economy of the plant in connexion 

 with the necessary supply of water. In some cases, as, for example, when 

 cell-walls or starch-grains are dissolved, the original organization is entirely 

 destroyed, while the material thus obtained becomes directly available to 

 the organism in a new form. Similar results may be produced by the 

 direct action of chemical reagents, but the plasma is extremely susceptible to 

 various injurious agencies, and if the action of any one of these is fatal, a pro- 

 found structural alteration takes place, such as always accompanies death. 



When the protoplasm dies, the non-living organized structures, such as 

 the cell-wall, starch-grains, crystalloids, &c., which it produced when alive ap- 

 pear to retain their original molecular structure. The optical appearances and 

 the power of swelling, at any rate, remain the same, and certain slight changes 

 of properties 3 which may take place are probably due to an infiltration of 

 certain constituents of the cell contents. It is nevertheless possible that 

 the cell-wall undergoes changes when the cell dies (independently of the 

 changes due to the death of the plasmatic threads which traverse it), although 

 these, have as yet escaped observation. Any changes produced by the 

 action of solvents, or of the chemical substances which led to the death 

 of the plasma, are of course quite different in character, and due to the 

 direct action of the agency in question. Even boiling water may not only 



1 On the conduction of sound, see Savart, Annales d. Chimie et Physique, 1829, T. XL, p. 113, 

 and physical textbooks. 



2 Ambronn, Ber. d. Sachs. Ges. d. Wiss., Bot., 1891, p. 394. 



3 Such as caused by staining or the absorption of dyes. See Nageli, Bot. Zeitung., 1881, p. 649. 



G 2 



