28 Tannin in the Fruit of the Persimmon [Sept. 



to Stretch the cell-wall beyond the breaking point so that, in some 

 fruits at least, one may find tannin-cells broken out in the fashion 

 already described, on the addition of water. Inasmuch as the 

 swelling is, in the nndisturbed fruit, a slow process, accompanied 

 by digestion of the cell-wall which results in weakening it in nu- 

 merous places, it more frequently happens that the tannin-mass 

 breaks out at as many points (fig. 24). It is evident that, during 

 a certain phase of change in the already overripe fruit, the 

 tannin-masses, as previously said on page 21 absorb water from 

 the pectose Solution resulting from the digestion of the middle 

 lamella. The consequent swelling forces out the free tannin, and 

 when pulp at this time is examined, the evidence of this is seen in 

 the complete membranes or in fragments of them, still attached to 

 (fig. 25), or broken away from, the tannin-cells. The same process 

 may be observed under the high power, and every detail of the 

 growth and change of shape followed, in preparations made by 

 covering a droplet of the pulp and adding a little water or fruit 

 Juice. In the course of a half-hour a great variety of precipitation 

 membranes will be formed.^^ 



There is thus afforded direct evidence that, during this phase of 

 ripening,^" some of the soluble tannin combines with substances 

 outside of the cells in which it was secreted; Bigelow, Gore and 

 Howard (1906, p. 700) rejected this view, but the reader will 

 recall that I have already pointed out that they found traces of 

 tannin in their extracts of quite ripe fruit. I venture the Suggestion 

 that a part of the " insoluble tannin " in the marc was the tannin 

 which had escaped as soluble tannin and is therefore to be distin- 

 guished quantitatively from the strictly " insoluble tannin " com- 

 bined with a second intracellular colloid. I have shown, further- 

 more, that this granulär matter is in such a combination with 

 tannin that neither alcohol, water nor dilute nitric acid destroys it, 

 nor is the tannin extracted by water or by alcohol. 



The extracellular tannin-colloid complex. The following ex- 



" One recalls the beautiful experiments of Le Duc (1910), the results of 

 which, in many instances, present features in common with these here described. 



"At the time of edibility, when the amount of free tannin is for the first 

 time not sufficient to produce astringency, the fruit has not passed into the con- 

 dition when the tannin extrudes as a result of the spontaneous swelling of the 

 tannin-masses, if indeed this always occurs. 



