PHYSIOLOGY OF THE RED MANGROVE. 645 



same substances in the ripening fruits of the Japanese persimmon 

 considers the tannin decrease in the ripening- process to be due en- 

 tirely to the oxidation of tannin and that it does not at all contribute 

 to the formation of carbohydrates. His reason for this conclusion 

 is that in the conversion of tannin into carbohydrates more carbon 

 dioxide would have to be liberated than oxygen absorbed, whereas 

 in fruits the relation is the reverse. 



Moore^^® contributes the idea that tannins may play an important 

 part in the lignification of cell walls. Drabbel and Winterstein^-^ 

 make the suggestion that their role is important in cork formation, 

 while Van Wisselingh^^*' has given the latest suggestion in that they 

 help materially in the formation of cellulose in some plants as 

 Spirogyra. The bulk of facts known, however, about tannins do 

 not lead one to suppose that they are used up in the plant generally 

 since they are left in parts discarded by plants, as fallen leaves and 

 not translocated, but even this does not assume much significance 

 since sugar and starch, etc., are also often found in fallen leaves, 

 and as Haas and HilF^^ remark, "A consideration of other facts 

 does not tend to support the idea of tannin being of the nature of a 

 reserve food." " Hillhouse,^^" for example, found that if a fuchsia 

 having an abundant supply of tannin be grown in the dark there is 

 no diminution in the substance in question." 



Notwithstanding the conflicting opinions regarding tannin and 

 the role it plays in the plant's physiology, it was decided to make a 

 series of experiments on the tannin of the hypocotyl of young seed- 

 lings, since in these storage organs it occurs in such great abundance 

 together with starch. With the hypothesis that perhaps the tannin 

 of the hypocotyl is broken down to form sugar as the growth of 

 the seedling proceeds, by the action of some enzyme as tannase, 

 tests were made for such an enzyme and also on the relative reac- 

 tion for dextrose and tannic acid. About ninety-five tests were 



128 Moore, A., Journal Linn. Soc, London, Bot. 27, 1891, p. 527. 



129 Drabbel, A., and Winterstein, E., Biochemical Journal, 2, 1906, p. 96. 



130 Van Wisselingh, C., Konen Akad van Wetensch. Amsterdam, 1910, 

 p. 685. 



131 Haas, P., and Hill, T. G., " Chemistry of Plant Products," London, 

 1913, p. 219. 



132 Hillhouse, B., Midland Naturalist, 1887-1888. 



