124 



MISSOURI BOTANICAL GARDEN. 



bruising 



masses of 



but 



with the idioplast layer. Aside from this, they are not at 

 all constant in position. Wherever the surface of the fruit 

 has been slightly damaged by pressure, as shown by brown- 

 ish coloration, one may generally find more extensive injec- 

 tion of the intercellular spaces beneath than elsewhere. 

 Where actual wounding and tearing of the tissues have inter- 

 vened, there may be observed a still more pronounced ap- 

 pearance of the tannin in question. Whether however the 

 injection of the intercellular spaces is due to an excretion 

 or to rupture of the tannin-containing cells there is no evi- 

 dence to decide. Vinson has observed that mature dates 

 rupture on being placed in certain fluids, and this occurred 

 in some of my own material, as well as some shrinkage at 

 times. The unequal pressures that are set up would probably 

 be sufficient to bring about the results described. 



Similar injection of the intercellular spaces frequently 

 occurs along the sutural tract, in contact with the idiopl asts 

 occurring there (f. 11). 



Mesocarp; endocarp. The line of delimitation between 



mesocarp and endocarp 



mak 



It will, however, 



somew 



may 



the seed as the endocarp. This 

 ing of from one to several cell-layers in thickness. The cells 

 are somewhat elongated with square, oblique or irre«iilar 

 s, occasionally sclerosed, and not infrequently, as Pond 

 (1907) discovered by chemical methods, contain tannin 

 which is similar to that found in the idioplasts. 



The mesocarp embraces two zonal regions, the outer and 

 inner. The outer mesocarp shows no peculiar anatomical 

 changes in the later period of development. That sector 

 of it which includes the tissues along the line of fusion 

 contains a good many scattered idioplasts, similar in all 

 respects to those of the periclinal zone, except that they are 

 more or less elongated. The closer they lie to the seed, the 

 greater their length; so great, indeed, that thev are onlv 



