Tannin in Persimmons. 3 



most ectocarp layer. The cells are irregular in shape, and are 

 characterized by very numerous slender pores. Aside from this 

 detail, the ectocarp in the persimmon simulates that in the date 

 very closeh-. In the persimmon it scarcely exceeds 0.2 mm. in 

 thickness. 



Mesocarp. Aside from the vascular tissue, this portion of 

 the fruit is composed of two kinds of cells, ordinary parenchyma 

 and tannin cells, or idioplasts. There appears to be no ground 

 for regarding these cells as physiologically identical at first with 

 the non-tanniferous parenchyma or pulp-cells, as I shall call 

 them hereafter. Although they may be difficult to distinguish 

 optically, at an early stage, just as the Anlaqen of different organs, 

 they are as definitely specialized cells as raphide idioplasts are. 

 I emphasize this point, since the position has been taken that, 

 during ripening, there occurs within certain cells a segregation 

 or condensation of tannin previously distributed throughout 

 the parenchyma (Howard, 1906). I have examined fruits 

 during the whole period of development, using copper acetate, 

 and Vinson's method of fixation by means of ethyl nitrite, and 

 at all times the tannin cells are clearly distinct from the pulp 

 cells, while these are entirely devoid of tannin. If, however, 

 sections are cut for microscopic examination from fresh, unfixed 

 material the dislocation of tannin renders it impossible to arrive 

 at this conclusion, unless great care is exercised. The rupturing 

 of the tannin cells results in the spreading of the tannin-fluid so 

 as to confuse observation when a tannin -testing agent is applied. 

 In order to get a clear conception of the distribution of tannin 

 in the unripe fruit the tissues must be fixed suitably before sec- 

 tions are cut. 



The shape of the tannin cells difi'ers to some degree in the 

 various species. Howard has stated the pertinent facts clearly, 

 and has published excellent photographs (1906). It should be 

 said that although the distinctions apply in a broad way, the 

 tannin cells near the vascular tracts are long and slender in ail 

 species. The distribution of these cells in the mesocarp is well 

 shown by Vinson's photograph, published in the Botanical 

 Gazette (49: 222). 



Endocarp. This region may be recognized as a translucent 

 zone entirely free from tannin cells, except that the epidermal 

 cells of the membrane lining the locule frequently contain 



