220 TANNINS 



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

 sures a sufficient supply of tannin in Spirogyrd, 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 Wisselingh 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 connexion, it may be mentioned 

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

 ments such as anthocyan and erythrophyll, for similar decom- 

 position products (compounds allied to the phenols) may be 

 obtained from each. 



The fact that some Fungi can make use of tannin as a food 

 material provided that it is not in excess, and the facts that 

 many are glucosides, and that oxidation readily takes place 

 with the ultimate formation of oxalic acid and carbon dioxide, 

 suggest that the substances under consideration may be reserve 

 food-material. 



Thus Schell, while acknowledging that tannin may some- 

 times be a bye-product of metabolism, considered that at other 

 times it might be used up in the construction of higher com- 

 pounds which would serve as food. He found that, in the 

 germination of the oil-containing seeds of Echium vulgare and 

 other Boraginaceae, as the oil is used up the tannin begins 

 to play a part in the constructive metabolism and gradually 

 diminishes in amount. Further, if such seeds be germinated 

 in the light the tannin increases in quantity. For these and 

 other reasons he concluded tftat such a use of tannin only ob- 



