102 THE MECHANISM OF ABSORPTION AND TRANSLOCATION 



regulates its intercourse with the external world, and hence, as might be 

 expected, the plasmatic membranes of different plants exhibit certain specific 

 differences and peculiarities. Apparently it is by temporary or permanent 

 alterations in the specific nature of the plasmatic membrane that an 

 absorption (or excretion) of a particular substance may be temporarily or 

 permanently permitted or prevented. There can be no doubt that the 

 physiological properties of the living ectoplasmic membrane are capable 

 of much more marked alteration or modification than are those of the dead 

 cell-wall immediately enclosing it. This is especially the case, owing to 

 the fact that the component micellae of the plasmatic membrane may be 

 loosened from their neighbours and carried away to the internal plasmatic 

 layers. Many facts indicate that frequently a change in the diosmotic 

 properties of the living cell is the means by which a particular result is 

 produced, although at present this statement is incapable of absolute proof. 

 It is always possible that a change in the diosmotic properties of the 

 plasmatic membranes may affect only one particular substance, while, with 

 regard to all others, the protoplast may appear to have the same diosmotic 

 properties as before. No difference of osmotic properties can be detected 

 in most cases between the living protoplast and the isolated vacuolar 

 membrane (Sects. 22, 108), for all dyes which are capable or incapable of 

 diosmosing through the protoplast are capable or incapable, as the case 

 may be, of passing through the vacuolar membrane also. Free acids and 

 alkalies give similar results, and as far as plasmolytic methods may be 

 trusted, the same is true for KNO 3 , Na Cl, and many other substances 1 . 



Imbibition and diosmosis are always dependent upon the nature of 

 the membranes or lamellae to be traversed, no matter whether these are 

 composed of solid or fluid substance. Hence infiltration of the lamellae by 

 another substance may markedly affect their diosmotic properties. The 

 cuticle affords a striking example of the utilization of this peculiarity by 

 the plant. 



In treating of the absorption of fats and oils, we have seen that the 

 infiltration of the separating membrane with another substance (phosphate 

 of sodium, &c.) renders a passage through the membrane possible, and 

 finely emulsified oil may pass through the cell-wall without any actual 

 solution being necessary, while slight mechanical pressure may suffice to 

 squeeze oil drops and solid bodies of measurable diameter through the 

 plasmatic membrane, which closes behind them, just as a film of oil closes 

 over a needle which has passed through it. Hence those substances which 



1 Pfeffer, 1. c., where it is also shown that the action of chloroform, or a deficiency of oxygen, &c., 

 does not prevent the absorption of aniline dyes. For these results attention only is paid to those 

 cases in which the plasmatic membranes are still living and plastic. Puriewitsch and Czapek have 

 recently shown that treatment with chloroform may produce a depressant effect on diosmosis 



(Sect. 1 08). 



