SEEDED FRUITS IN THE PERSIMMON 113 



mal hastening of a single process, namely the coagulation of the 

 emulsion colloid wdth which the tannin is associated. I have shown 

 that carbon dioxide in major dosage may do this. A sufficiently 

 rapid accumulation of this gas in the tissues, either locally or gen- 

 erally, is quite thinkable and would readily suggest itself as the 

 explanation of the changes in the region of a large growing seed, 

 such as that of the persimmon, but unfortunately this view does 

 not accord with all the facts. It is, however, at the moment 

 the only plausible theory, and any other that might be offered 

 would harmonize still less with our present knowledge of fact. 



II. A VISUAL METHOD FOR ESTIMATING 

 ASTRINGENCY 



(A Preliminary Note) 



The following method is based on the observation that the 

 degree of astringency depends on the degree of adsorption of the 

 tannin by the X-cellulose. Since this increases during ripening, 

 the amount of tannin which can be adsorbed by another sub- 

 stance decreases. The other substance, according to previous 

 experience, is that of the mucous membranes. If, however, a 

 suitable adsorbing agent {e.g. pure cellulose in the form of filter 

 paper) be substituted for the mucous membranes, a partition of 

 the tannin will occur, the amount being taken up by the filter 

 paper being directly proportional to the astringency. The pro- 

 cedure is as follows: 



Slightly moistened filter paper is laid on a cut surface of the 

 fruits to be examined, and allowed to remain for a given length 

 of time. Upon removal a tannin reagent giving a colour reac- 

 tion is applied and there^dth an image is developed. The strength 

 of the image (which appears as a contact print of the tannin- 

 tissues) will be great or small according to the amount of tannin 

 adsorbed. The results which have been obtained enable one 

 to determine astringency and non-astringency quite as accu- 

 rately as, and much more comfortably than, by tasting. 



