240 BOTANY 



Seifriz, using a wide variety of examples, investigated this matter 

 of viscosity. They employed the eggs of Fucus, pollen tubes, 

 and Plasmodia of myxomycetes, and found the cytoplasm to be of 

 the consistency of a liquid. There was a rapid increase in the 

 viscosity of the eggs of Fucus towards the end of the ripening 

 process, but at fertilisation there was a return to the liquid 

 condition once more. The matter of cytoplasmic viscosity seems 

 to be variable and to vary with different conditions of development. 

 In the myxomycete plasmodium a sol condition was ascertained, 

 whereas in the hyphae of the mould Rhizopus, the cytoplasm was 

 apparently in the gel state and was claimed to have the consistency 

 of bread dough. Heilbrunn, however, has criticised the various 

 methods that have been employed from time to time to measure 

 the viscosity of the living cell and claimed that the microdissection 

 method was by no means ideal for this purpose. " For the 

 measurement of viscosity, the microdissection method can at the 

 best give only indications of gross differences in viscosity. And 

 even for these it is more or less uncertain." The introduction of 

 the needle into the cell involves injury, and this might possibly 

 alter the viscosity of the cytoplasm. The early experiments of 

 Heilbrunn himself on the endodermal cells of Viciafaba, in which 

 he observed the fall of starch grains under the influence of gravity 

 and compared the rate with their fall in water, seemed to show that 

 the viscosity of the cytoplasm was about eight times that of water. 

 Later he introduced a second method, in which small iron rods 

 were placed in the plasmodium of a myxomycete. The Plasmo- 

 dium was then placed under the influence of a magnetic field from 

 an electric magnet. The extent to which the rods turned under 

 these conditions depended on the viscosity of the cytoplasm. 

 Here the results indicated that the viscosity was from nine to 

 eighteen times that of water. 



Weber made the claim that the form taken by some plant cells, 

 e.g., Spirogyra, when plasmolysed, depends on viscosity and that 

 the form of plasmolysis can be taken as an index of viscosity. 

 There can be little doubt that the viscosity of the li\'ing cell varies 

 at different times in its life. But it is important to remember that 

 it is physical structure and not viscosity that determines whether 



