4 . The Plant World. 



tannin. The cells, other than these, are identical, to all appear- 

 ances, with the pulp cells, are regularly but only slightly elon- 

 i^ated, and are fliced with their longer axes directed toward the 

 locule. The endocarp is peculiar in not becoming mushy or 

 in any degree dtliquescent in the Japanese variety during ripen- 

 ing In our own species sufficient disintegration takes place so 

 that only a thin membrane of gelatinous consistence remains, 

 usually enwrapping the seed. This resistance by the endocarp 

 to a change which overtakes the mesocarp, from which the former 

 is not sharp y separated, is remarkab e. The mesocarp becomes 

 quite watery during ripening, in contrast to a mushy-granular 

 condition in the American. This is due to the breaking down 

 of the midd e lame la (Howard) resulting in the formation of 

 substances which act plasmolytically upon the cells, which, in 

 a ripe fruit, are collapsed, with their plasmatic membranes 

 shrunken well toward the center of the cell. This is true of both 

 pulp and tannin cells, but the latter do not show the effect so 

 evidently since the vacuole is occupied by tannin, or rather a 

 tannin-containing mass which may perhaps be identified with Af 

 Klerker's "tannin- vesicle." The fact that the tannin-cells as 

 such are plasmolysed in the ripe fruit is of importance in view of 

 their behavior upon treatment with water or saliva, to which 

 reference will be made. We may now focus attention upon the 

 mesocarp cells, as at the present moment we are especially con- 

 cerned with these. 



The cells of the viesocarp. The pulp cells are very thin 

 walled, and before ripening are firmly bound together. No sign 

 of plasmolysis appears. The very thin plasmatic membrane, 

 the nucleus suspended near the center of the cell, and the radiat- 

 ing threads of protoplasm are all normal and in position. Spindle 

 shaped coloring bodies (carotin) are distributed through the 

 protoplasm. 



The tannin cells have thicker walls with groups of wide pores 

 on the facets opposed to contiguous pulp cells. These are 

 brought out clearly by means of iodine, to which the wall reacts 

 Llue. Adjacent tannin cells are attached to each other by 

 means of bridges (Howard) between which are intercellular 

 spaces. The importance of these spaces in relation to possible 

 physiological phenomena within the tannin cells would seem to 

 be unquestionable, but we have no precise light on the matter. 



