648 BOWMAN— ECOLOGY AND 



each one was quickly added ten drops of concentrated HCl. A deep 

 blue color, in varying degrees of intensity dependent on the amount 

 present, indicated the dextrose. 



The tannin was tested for by means of Hager's Test, after ex- 

 perimenting with various tests, as Gayard's, Grigg's, Oliver's, 

 Vogel's, Watson's and Young's, the one selected was found to be 

 the best for the material in hand, just as Huizinga's Test for Dex- 

 trose seemed to be the best of nine other tests tried. The test for 

 tannin consisted in placing one c.c. in each of a series of test tubes 

 and diluted with five c.c. of distilled water. To each was then 

 added one c.c. of a saturated solution of hydrogen sodium phosphate 

 (NaoHP04) and a single drop of rather strong ferric chloride 

 solution, when a precipitate of a bluish violet color occurred in pro- 

 portion to the amount of tannin present in the tubes. 



Why these tests and reagents seemed to be the best for testing 

 the substances in question in the mangrove extracts is not known, 

 but it probably depends on the peculiar composition of Rhisophora 

 tannin, etc. The tannin of the red mangrove, according to the classi- 

 fication of Haas and Hill, belongs to the Pyrocatechol Group, but 

 as these authors state on account of the incomplete status of knowl- 

 edge regarding the tannins as a whole and of the chemistry of this 

 group in particular, it is a very difficult matter to classify them prop- 

 erly. According to Kraemer^^'' the tannins of the above group pro- 

 duce protocatechuic acid on fusion with potassium hydroxide and 

 phlobaphenes on treatment with acids. A very careful analysis of 

 the bark extract of RJiisophora was made by Trimble.^^^ His re- 

 sults showed that no gallic acid was present and that in the dry 

 total tannic acid occurred to the amount of 23.92 per cent, and 

 mucilage 1.72 per cent., glucose .81 per cent., albuminoids 7.02 per 

 cent., starch 4.27 per cent, and cellulose 27.49 per cent. Although 

 perhaps the reagents were adapted to this group of pyrocatechol 

 tannins, the results of the tests signify merely a relative value, for 

 the quantities of the substances in question. Thus the comparison 

 colorimetrically of the individual tests of each plant with that of a 



^^" Kraemcr, H., "Applied and Economic Botan}-," Pliiladelphia, 1914, 

 p. 204. 



138 Xrimble, H., "Mangrove Taimin," Univ. of Pouia. Bot. Lab. Contri- 

 buiions, Vol. i, No. i, 1892, p. 50. 



