2 The Plant World, 



That this takes place is the fact; the explanation of it has been 

 the subject of some inquiry, but with little enlightenment, at 

 least with respect to the two fruits above named. The problem 

 divides itself naturally and trenchantly into two parts; one deal- 

 ing with fruits from which, during ripening, the tannin disap- 

 pears by chemical change, as oxidation; and that dealing with 

 cases in which the tannin becomes "insoluble" but apparently 

 unaltered chemically. The date and persimmon are of the latter 

 kind. But wherein does this insolubility consist.-* To this 

 question no adequate answer has been given. That it unites 

 with some other substance ,as "marc," has appeared possible, 

 but no evidence is forthcoming that this is the case. (Bigelow, 

 Gore, and Howard, 1906). That the change does not involve a 

 metastasis of the tannin molecule (Vinson, 1910) can hardly be 

 denied, nor that some change has intervened to alter the physical 

 potentialities of the substance. It is, indeed, just this latter cir- 

 cumstance which baffles the student, since physical tests no 

 longer apfly, e. g., astringent tannin becomes non-astringent. 



The purpose of the present paper is to re-open the problem 

 in the light of a study of the persimmon during ripening. The ac- 

 count which follows will be found to disagree at some points with 

 those of other observers, and at others to supplement them. 

 The work, which is by no means yet complete, has been intended 

 to supplement that done on the date (Lloyd, 1910). Since fresh 

 materi^-1 of ripening stages was not available, the conclusions 

 reached were of necessity inadequate. It is expected that the 

 coming season will afford the opportunity of further study of this 

 form. 



Histology of the Persimmon Fruit. 



The pericarp is readily divided into the usual three regions, 

 ecto-, meso-, and endocarp. The thickness of each varies in our 

 native and exotic species, but these differences are of 

 minor moment in the present connection. Evident physiologi- 

 cal differences, which will be referred to beyond, are displayed 

 during ripening. 



Ectocarp. The ectocarp consists of a heavy cuticularized 

 epidermis of tanniferous cells, the guard cells offering no excep- 

 tion. Four to six layers of more or less compressed frequently 

 tanniferous parenchyma cells intervene until a zone of stone cells 

 is reached. This may be regarded, for convenience, as the inner- 



