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Botany. — "•Determination of the action of poisons on plants." By 

 Prof. E. Verschaffelt. (Communicated by Prof's. C. A. Lobry 

 DE Bruyn and Hugo de Vries.) 



When a part of a living organ of a land-plant is placed in water 

 it usually absorbs water on account of the well-known osmotic 

 properties of the protoplasm and this absorption goes on until the 

 cell- walls allow of no further extension. The accompanying increase 

 in volume and the phenomena of tension in the tissue which may 

 result therefrom, have, since Hugo de Vries laid the foundations of 

 the subject, given rise to many an investigation which it will be 

 superfluous to mention here again. Evidently this absorption of 

 water will also cause the weight of the fragment of tissue to increase 

 and it is easily understood that fairly considerable differences in 

 weight will arise as soon as the organ is somewhat rich in parenchyra. 



All this only happens however as long as the part of the plant 

 is alive. When a part of an organ that has been previously killed 

 is placed in water, no more water is absorbed; on the contrary, 

 since the semipermeability of the protoplasm has been destroyed, 

 the dissolved substances of the cell-sap diffuse out; with them part 

 of the water that stretches the cell-wall leaves the fragment of tissue, 

 and this latter diminishes in weight as well as in volume. 



Hence it seems possible, by determining the changes in weight, 

 subsequent upon placing a plant-organ in water, to decide whether 

 this latter is alive or dead. If it turns out that no other circum- 

 stances have a disturbing influence, we should have a new criterion 

 for determining the lethal limit of measurable external circumstances, 

 besides the diffusion of colouring matter at the death of plant-cells^), 

 used by Hugo de Vries, and the non-appearance of the plasmolytic 

 phenomenon, recently applied by A. J. J. van de Velde'). In order 

 to test the practicableness of the method I tried to determine in 

 this way the toxic limit of a few substances and it seems to me 

 that this has been successful. Not every arbitrarily chosen plant-organ 

 can be expected to lend itself equally well for these experiments; 

 most of them proved serviceable, however, and as very fit for this 

 purpose I mention the potato-tuber, beetroot, fleshy leaves of Aloe, 

 juicy leaf-stalks like those of Begonia, Rheum and other plants. 



One example may illustrate the proceeding and give an idea about 

 the observed differences in weight. 



1) Arch. Née7rl. VI, 1871. 



2) Transactions of the four first Flemish Physical and Medical Congresses 

 (Dutch). 



