274 TANNINS 



concluded that tannin is an intermediate product in resin 

 formation. 



Tannin is not uncommon in unripe fruits, and the amount 

 of these astringent substances diminishes during ripening. 



According to Bassett * " the amount of tannin in fruits 

 varies with certain factors, such as injury, length of time be- 

 tween removal from tree and analysis, etc. The presence and 

 relative amount of this tannin or tannin-like body is con- 

 trolled by the presence of certain enzymes which vary in 

 amount and activity during the growth of these fruits." 



Buignet, from the fact of the diminution of tannin and 

 starch which occurs concurrently with the increase in sugar, 

 considered that the sugar in the ripe fruit (e.g. Musa) is 

 formed from these two substances. This opinion, however, is 

 not held by Gerber who investigated the same phenomenon. 

 In Diospyros Kaki he found the young fruit to be very 

 astringent, but not so the ripe fruit. He considers that the 

 tannins disappear by complete oxidation without the forma- 

 tion of carbohydrates. One reason for his opinion is that in 

 the conversion of tannin into carbohydrate more carbon dioxide 

 would have to be liberated than oxygen absorbed, whereas in 

 fruits the relation is the reverse. 



Other suggestions regarding the value of tannin are not 

 wanting ; thus Moore f states that it may play an important 

 part in the lignification of cell walls. 



Drabble and Nierenstein % have come to the conclusion 

 that tannins play an important part in cork formation, and 

 are acted upon in the plant by formaldehyde and acids and 

 are precipitated in the walls of the cork cells. 



Van Wisselingh has published certain observations from 

 which he concludes that tannin plays an important part 

 in the formation of cell walls in certain cases, for instance 

 Spirogyra. He does not consider it a reserve food-material 

 as such, but rather a soluble substance which the plant 



* Quoted from the footnote appended to a paper on the Toxicity of 

 Tannin by Cook and Taubenhaus ; " Delaware Coll. Agric. Exp. Station," 

 Bull. 91, 191 1. 



t Moore : loc. cit. 



X Drabble and Nierenstein : " Biochem. Journ.," 1906, 2, 96. 



