PHYSIOLOGY 275 



makes use of in elaborating other materials. This con- 

 clusion is in agreement with the opinions held by Wiegand 

 and published in 1862. Van Wisselingh worked with Spirogyra, 

 and the main facts on which he based his conclusions are as 

 follows : Cells which are about to conjugate are rich in tannin, 

 and as the process of conjugation proceeds, there is a gradual 

 diminution in the amount of this substance, so that the mature 

 zygospore contains nothing more than mere traces. If con- 

 jugation be interrupted at an early stage, there is still 

 an increase of tannin, so that when death results there is 

 relatively a large quantity present. This accumulation may 

 be used as an argument in support of the view that tannin is 

 a waste product. Van Wisselingh, however, remarks that this 

 should not be a source of wonder, for in this case " it is not 

 the intention of Nature that it should be wasted. Nature en- 

 sures a sufficient supply of tannin in Spirogyra, because this 

 substance is required in development, as for instance in conju- 

 gation and spore-formation. The occasional failure to conjugate 

 as a result of which much tannin is lost, does not prove that 

 it is a waste product and not a plastic material." 



The author in question also found that a diminution of 

 tannin occurred during the formation of the cell wall after 

 nuclear division, and if the tannin were precipitated during the 

 earliest phases of cell division, the cell wall was not formed 

 although the nucleus divided into two quite normally. Clado- 

 phora, which does not contain tannin, was used as a control ; 

 it was found that by keeping the filament in a solution of anti- 

 pyrine, the reagent used in the experiment on Spirogyra, the 

 cell-wall formation was not disturbed. 



It must be mentioned that Van WisseUngh does not claim 

 that tannin is the only substance used in cell-wall formation, 

 nor does he maintain that the only physiological significance 

 of tannin is its use as a plastic material. 



Finally, in this particular connection, it may be mentioned 

 that tannin may play a part in the formation of various pig- 

 ments such as anthocyan, for similar decomposition products 

 (compounds allied to the phenols) may be obtained from 



each. 



18* 



